Classification.

Vitamins are classified as either water-soluble or fat-soluble. In humans there are 13 vitamins: 4 fat-soluble (A, D, E, and K) and 9 water-soluble (8 B vitamins and vitamin C). Water-soluble vitamins dissolve easily in water and, in general, are readily excreted from the body, to the degree that urinary output is a strong predictor of vitamin consumption. Because they are not as readily stored, more consistent intake is important. Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats). Vitamins A and D can accumulate in the body, which can result in dangerous hypervitaminosis. Fat-soluble vitamin deficiency due to malabsorption is of particular significance in cystic fibrosis.

Anti-vitamins.

Anti-vitamins are chemical compounds that inhibit the absorption or actions of vitamins. For example, avidin is a protein in raw egg whites that inhibits the absorption of biotin; it is deactivated by cooking. Pyrithiamine, a synthetic compound, has a molecular structure similar to thiamine, vitamin B, and inhibits the enzymes that use thiamine.

Biochemical functions.

Each vitamin is typically used in multiple reactions, and therefore most have multiple functions.

On fetal growth and childhood development.

Vitamins are essential for the normal growth and development of a multicellular organism. Using the genetic blueprint inherited from its parents, a fetus develops from the nutrients it absorbs. It requires certain vitamins and minerals to be present at certain times. These nutrients facilitate the chemical reactions that produce among other things, skin, bone, and muscle. If there is serious deficiency in one or more of these nutrients, a child may develop a deficiency disease. Even minor deficiencies may cause permanent damage.

On adult health maintenance.

Once growth and development are completed, vitamins remain essential nutrients for the healthy maintenance of the cells, tissues, and organs that make up a multicellular organism; they also enable a multicellular life form to efficiently use chemical energy provided by food it eats, and to help process the proteins, carbohydrates, and fats required for cellular respiration.

Intake.

Sources.

For the most part, vitamins are obtained from the diet, but some are acquired by other means: for example, microorganisms in the gut flora produce vitamin K and biotin; and one form of vitamin D is synthesized in skin cells when they are exposed to a certain wavelength of ultraviolet light present in sunlight. Humans can produce some vitamins from precursors they consume: for example, vitamin A is synthesized from beta carotene; and niacin is synthesized from the amino acid tryptophan. The Food Fortification Initiative lists countries which have mandatory fortification programs for vitamins folic acid, niacin, vitamin A and vitamins B1, B2 and B12.

Deficient intake.

The body's stores for different vitamins vary widely; vitamins A, D, and B are stored in significant amounts, mainly in the liver, and an adult's diet may be deficient in vitamins A and D for many months and B in some cases for years, before developing a deficiency condition. However, vitamin B (niacin and niacinamide) is not stored in significant amounts, so stores may last only a couple of weeks. For vitamin C, the first symptoms of scurvy in experimental studies of complete vitamin C deprivation in humans have varied widely, from a month to more than six months, depending on previous dietary history that determined body stores.  Deficiencies of vitamins are classified as either primary or secondary. A primary deficiency occurs when an organism does not get enough of the vitamin in its food. A secondary deficiency may be due to an underlying disorder that prevents or limits the absorption or use of the vitamin, due to a "lifestyle factor", such as smoking, excessive alcohol consumption, or the use of medications that interfere with the absorption or use of the vitamin. People who eat a varied diet are unlikely to develop a severe primary vitamin deficiency, but may be consuming less than the recommended amounts; a national food and supplement survey conducted in the US over 2003-2006 reported that over 90% of individuals who did not consume vitamin supplements were found to have inadequate levels of some of the essential vitamins, notably vitamins D and E.  Well-researched human vitamin deficiencies involve thiamine (beriberi), niacin (pellagra), vitamin C (scurvy), folate (neural tube defects) and vitamin D (rickets). In much of the developed world these deficiencies are rare due to an adequate supply of food and the addition of vitamins to common foods. In addition to these classical vitamin deficiency diseases, some evidence has also suggested links between vitamin deficiency and a number of different disorders.

Excess intake.

Some vitamins have documented acute or chronic toxicity at larger intakes, which is referred to as hypertoxicity. The European Union and the governments of several countries have established Tolerable upper intake levels (ULs) for those vitamins which have documented toxicity (see table). The likelihood of consuming too much of any vitamin from food is remote, but excessive intake (vitamin poisoning) from dietary supplements does occur. In 2016, overdose exposure to all formulations of vitamins and multi-vitamin/mineral formulations was reported by 63,931 individuals to the American Association of Poison Control Centers with 72% of these exposures in children under the age of five. In the US, analysis of a national diet and supplement survey reported that about 7% of adult supplement users exceeded the UL for folate and 5% of those older than age 50 years exceeded the UL for vitamin A.

Effects of cooking.

The USDA has conducted extensive studies on the percentage losses of various nutrients from food types and cooking methods. Some vitamins may become more "bio-available" – that is, usable by the body – when foods are cooked. The table below shows whether various vitamins are susceptible to loss from heat—such as heat from boiling, steaming, frying, etc. The effect of cutting vegetables can be seen from exposure to air and light. Water-soluble vitamins such as B and C dissolve into the water when a vegetable is boiled, and are then lost when the water is discarded.

Recommended levels.

In setting human nutrient guidelines, government organizations do not necessarily agree on amounts needed to avoid deficiency or maximum amounts to avoid the risk of toxicity. For example, for vitamin C, recommended intakes range from 40 mg/day in India to 155 mg/day for the European Union. The table below shows U.S. Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for vitamins, PRIs for the European Union (same concept as RDAs), followed by what three government organizations deem to be the safe upper intake. RDAs are set higher than EARs to cover people with higher than average needs. Adequate Intakes (AIs) are set when there is not sufficient information to establish EARs and RDAs. Governments are slow to revise information of this nature. For the U.S. values, with the exception of calcium and vitamin D, all of the data date to 1997-2004.  EAR US Estimated Average Requirements.  RDA US Recommended Dietary Allowances; higher for adults than for children, and may be even higher for women who are pregnant or lactating.  AI US and EFSA Adequate Intake; AIs established when there is not sufficient information to set EARs and RDAs.  PRI Population Reference Intake is European Union equivalent of RDA; higher for adults than for children, and may be even higher for women who are pregnant or lactating. For Thiamin and Niacin the PRIs are expressed as amounts per MJ of calories consumed. MJ = megajoule = 239 food calories.  UL or Upper Limit Tolerable upper intake levels.  ND ULs have not been determined.  NE EARs have not been established.

Supplementation.

In those who are otherwise healthy, there is little evidence that supplements have any benefits with respect to cancer or heart disease. Vitamin A and E supplements not only provide no health benefits for generally healthy individuals, but they may increase mortality, though the two large studies that support this conclusion included smokers for whom it was already known that beta-carotene supplements can be harmful. A 2018 meta-analysis found no evidence that intake of vitamin D or calcium for community-dwelling elderly people reduced bone fractures.  Europe has regulations that define limits of vitamin (and mineral) dosages for their safe use as dietary supplements. Most vitamins that are sold as dietary supplements are not supposed to exceed a maximum daily dosage referred to as the tolerable upper intake level (UL or Upper Limit). Vitamin products above these regulatory limits are not considered supplements and should be registered as prescription or non-prescription (over-the-counter drugs) due to their potential side effects. The European Union, United States and Japan establish ULs.  Dietary supplements often contain vitamins, but may also include other ingredients, such as minerals, herbs, and botanicals. Scientific evidence supports the benefits of dietary supplements for persons with certain health conditions. In some cases, vitamin supplements may have unwanted effects, especially if taken before surgery, with other dietary supplements or medicines, or if the person taking them has certain health conditions. They may also contain levels of vitamins many times higher, and in different forms, than one may ingest through food.

Governmental regulation.

Most countries place dietary supplements in a special category under the general umbrella of "foods", not drugs. As a result, the manufacturer, and not the government, has the responsibility of ensuring that its dietary supplement products are safe before they are marketed. Regulation of supplements varies widely by country. In the United States, a dietary supplement is defined under the Dietary Supplement Health and Education Act of 1994. There is no FDA approval process for dietary supplements, and no requirement that manufacturers prove the safety or efficacy of supplements introduced before 1994. The Food and Drug Administration must rely on its Adverse Event Reporting System to monitor adverse events that occur with supplements. In 2007, the US Code of Federal Regulations (CFR) Title 21, part III took effect, regulating Good Manufacturing Practices (GMPs) in the manufacturing, packaging, labeling, or holding operations for dietary supplements. Even though product registration is not required, these regulations mandate production and quality control standards (including testing for identity, purity and adulterations) for dietary supplements. In the European Union, the Food Supplements Directive requires that only those supplements that have been proven safe can be sold without a prescription. For most vitamins, pharmacopoeial standards have been established. In the United States, the United States Pharmacopeia (USP) sets standards for the most commonly used vitamins and preparations thereof. Likewise, monographs of the European Pharmacopoeia (Ph.Eur.) regulate aspects of identity and purity for vitamins on the European market.

Naming.

The reason that the set of vitamins skips directly from E to K is that the vitamins corresponding to letters F–J were either reclassified over time, discarded as false leads, or renamed because of their relationship to vitamin B, which became a complex of vitamins.  The German-speaking scientists who isolated and described vitamin K (in addition to naming it as such) did so because the vitamin is intimately involved in the coagulation of blood following wounding (from the German word "Koagulation"). At the time, most (but not all) of the letters from F through to J were already designated, so the use of the letter K was considered quite reasonable. The table "Nomenclature of reclassified vitamins" lists chemicals that had previously been classified as vitamins, as well as the earlier names of vitamins that later became part of the B-complex.  The missing B vitamins were reclassified or determined not to be vitamins. For example, B is folic acid and five of the folates are in the range B through B. Others, such as PABA (formerly B), are biologically inactive, toxic, or with unclassifiable effects in humans, or not generally recognised as vitamins by science, such as the highest-numbered, which some naturopath practitioners call B and B. There are also nine lettered B complex vitamins (e.g., B). There are other D vitamins now recognised as other substances, which some sources of the same type number up to D. The controversial cancer treatment laetrile was at one point lettered as vitamin B. There appears to be no consensus on any vitamins Q, R, T, V, W, X, Y or Z, nor are there substances officially designated as vitamins N or I, although the latter may have been another form of one of the other vitamins or a known and named nutrient of another type.

History.

The value of eating certain foods to maintain health was recognized long before vitamins were identified. The ancient Egyptians knew that feeding liver to a person may help with night blindness, an illness now known to be caused by a vitamin A deficiency. The advancement of ocean voyages during the Renaissance resulted in prolonged periods without access to fresh fruits and vegetables, and made illnesses from vitamin deficiency common among ships' crews.  In 1747, the Scottish surgeon James Lind discovered that citrus foods helped prevent scurvy, a particularly deadly disease in which collagen is not properly formed, causing poor wound healing, bleeding of the gums, severe pain, and death. In 1753, Lind published his "Treatise on the Scurvy", which recommended using lemons and limes to avoid scurvy, which was adopted by the British Royal Navy. This led to the nickname "limey" for British sailors. Lind's discovery, however, was not widely accepted by individuals in the Royal Navy's Arctic expeditions in the 19th century, where it was widely believed that scurvy could be prevented by practicing good hygiene, regular exercise, and maintaining the morale of the crew while on board, rather than by a diet of fresh food. As a result, Arctic expeditions continued to be plagued by scurvy and other deficiency diseases. In the early 20th century, when Robert Falcon Scott made his two expeditions to the Antarctic, the prevailing medical theory at the time was that scurvy was caused by "tainted" canned food.  During the late 18th and early 19th centuries, the use of deprivation studies allowed scientists to isolate and identify a number of vitamins. Lipid from fish oil was used to cure rickets in rats, and the fat-soluble nutrient was called "antirachitic A". Thus, the first "vitamin" bioactivity ever isolated, which cured rickets, was initially called "vitamin A"; however, the bioactivity of this compound is now called vitamin D. In 1881, Russian medical doctor studied the effects of scurvy at the University of Tartu. He fed mice an artificial mixture of all the separate constituents of milk known at that time, namely the proteins, fats, carbohydrates, and salts. The mice that received only the individual constituents died, while the mice fed by milk itself developed normally. He made a conclusion that "a natural food such as milk must therefore contain, besides these known principal ingredients, small quantities of unknown substances essential to life." However, his conclusions were rejected by his advisor, Gustav von Bunge. A similar result by Cornelius Pekelharing appeared in a Dutch medical journal in 1905, but it was not widely reported.  In East Asia, where polished white rice was the common staple food of the middle class, beriberi resulting from lack of vitamin B was endemic. In 1884, Takaki Kanehiro, a British-trained medical doctor of the Imperial Japanese Navy, observed that beriberi was endemic among low-ranking crew who often ate nothing but rice, but not among officers who consumed a Western-style diet. With the support of the Japanese navy, he experimented using crews of two battleships; one crew was fed only white rice, while the other was fed a diet of meat, fish, barley, rice, and beans. The group that ate only white rice documented 161 crew members with beriberi and 25 deaths, while the latter group had only 14 cases of beriberi and no deaths. This convinced Takaki and the Japanese Navy that diet was the cause of beriberi, but they mistakenly believed that sufficient amounts of protein prevented it. That diseases could result from some dietary deficiencies was further investigated by Christiaan Eijkman, who in 1897 discovered that feeding unpolished rice instead of the polished variety to chickens helped to prevent a kind of polyneuritis that was the equivalent of beriberi. The following year, Frederick Hopkins postulated that some foods contained "accessory factors" — in addition to proteins, carbohydrates, fats "etc." — that are necessary for the functions of the human body. Hopkins and Eijkman were awarded the Nobel Prize for Physiology or Medicine in 1929 for their discoveries. In 1910, the first vitamin complex was isolated by Japanese scientist Umetaro Suzuki, who succeeded in extracting a water-soluble complex of micronutrients from rice bran and named it aberic acid (later "Orizanin"). He published this discovery in a Japanese scientific journal. When the article was translated into German, the translation failed to state that it was a newly discovered nutrient, a claim made in the original Japanese article, and hence his discovery failed to gain publicity. In 1912 Polish-born biochemist Casimir Funk, working in London, isolated the same complex of micronutrients and proposed the complex be named "vitamine". It was later to be known as vitamin B (niacin), though he described it as "anti-beri-beri-factor" (which would today be called thiamine or vitamin B). Funk proposed the hypothesis that other diseases, such as rickets, pellagra, coeliac disease, and scurvy could also be cured by vitamins. Max Nierenstein a friend and reader of Biochemistry at Bristol University reportedly suggested the "vitamine" name (from "vital amine"). The name soon became synonymous with Hopkins' "accessory factors", and, by the time it was shown that not all vitamins are amines, the word was already ubiquitous. In 1920, Jack Cecil Drummond proposed that the final "e" be dropped to deemphasize the "amine" reference, after researchers began to suspect that not all "vitamines" (in particular, vitamin A) have an amine component.  In 1930, Paul Karrer elucidated the correct structure for beta-carotene, the main precursor of vitamin A, and identified other carotenoids. Karrer and Norman Haworth confirmed Albert Szent-Györgyi's discovery of ascorbic acid and made significant contributions to the chemistry of flavins, which led to the identification of lactoflavin. For their investigations on carotenoids, flavins and vitamins A and B, they both received the Nobel Prize in Chemistry in 1937.  In 1931, Albert Szent-Györgyi and a fellow researcher Joseph Svirbely suspected that "hexuronic acid" was actually vitamin C, and gave a sample to Charles Glen King, who proved its anti-scorbutic activity in his long-established guinea pig scorbutic assay. In 1937, Szent-Györgyi was awarded the Nobel Prize in Physiology or Medicine for his discovery. In 1943, Edward Adelbert Doisy and Henrik Dam were awarded the Nobel Prize in Physiology or Medicine for their discovery of vitamin K and its chemical structure. In 1967, George Wald was awarded the Nobel Prize (along with Ragnar Granit and Haldan Keffer Hartline) for his discovery that vitamin A could participate directly in a physiological process.  In 1938, Richard Kuhn was awarded the Nobel Prize in Chemistry for his work on carotenoids and vitamins, specifically B and B.

History of promotional marketing.

Once discovered, vitamins were actively promoted in articles and advertisements in "McCall's", "Good Housekeeping", and other media outlets. Marketers enthusiastically promoted cod-liver oil, a source of Vitamin D, as "bottled sunshine", and bananas as a “natural vitality food". They promoted foods such as yeast cakes, a source of B vitamins, on the basis of scientifically-determined nutritional value, rather than taste or appearance. World War II researchers focused on the need to ensure adequate nutrition, especially in processed foods. Robert W. Yoder is credited with first using the term "vitamania", in 1942, to describe the appeal of relying on nutritional supplements rather than on obtaining vitamins from a varied diet of foods. The continuing preoccupation with a healthy lifestyle has led to an obsessive consumption of additives the beneficial effects of which are questionable.

Etymology.

The term "vitamin" was derived from "vitamine", a compound word coined in 1912 by the Polish biochemist Casimir Funk when working at the Lister Institute of Preventive Medicine. The name is from "vital" and "amine", meaning amine of life, because it was suggested in 1912 that the organic micronutrient food factors that prevent beriberi and perhaps other similar dietary-deficiency diseases might be chemical amines. This was true of thiamine, but after it was found that other such micronutrients were not amines the word was shortened to vitamin in English.

A vitamin is an organic molecule (or related set of molecules) that is an essential micronutrient which an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrients cannot be synthesized in the organism, either at all or not in sufficient quantities, and therefore must be obtained through the diet. Vitamin C can be synthesized by some species but not by others; it is not a vitamin in the first instance but is in the second. The term "vitamin" does not include the three other groups of essential nutrients: minerals, essential fatty acids, and essential amino acids. Most vitamins are not single molecules, but groups of related molecules called vitamers. For example, vitamin E consists of four tocopherols and four tocotrienols. Though some sources list fourteen by including choline, major health organizations list thirteen: vitamin A (as all-"trans"-retinol, all-"trans"-retinyl-esters, as well as all-"trans"-beta-carotene and other provitamin A carotenoids), vitamin B (thiamine), vitamin B (riboflavin), vitamin B (niacin), vitamin B (pantothenic acid), vitamin B (pyridoxine), vitamin B (biotin), vitamin B (folic acid or folate), vitamin B (cobalamins), vitamin C (ascorbic acid), vitamin D (calciferols), vitamin E (tocopherols and tocotrienols), and vitamin K (quinones).

Une vitamine est une substance organique, nécessaire en faible quantité (moins de 100 mg/jour - voir tableau ci-dessous) au métabolisme d'un organisme vivant, qui ne peut être synthétisée en quantité suffisante par cet organisme. Chaque organisme a des besoins spécifiques : une molécule peut être une vitamine pour une espèce et ne pas l'être pour un autre. C'est par exemple le cas de la vitamine C indispensable aux primates mais pas à la plupart des autres mammifères.


History.

The GFDL was released in draft form for feedback in September 1999. After revisions, version 1.1 was issued in March 2000, version 1.2 in November 2002, and version 1.3 in November 2008. The current state of the license is version 1.3.  The first discussion draft of the GNU Free Documentation License version 2 was released on September 26, 2006, along with a draft of the new GNU Simpler Free Documentation License.  On December 1, 2007, Wikipedia founder Jimmy Wales announced that a long period of discussion and negotiation between and amongst the Free Software Foundation, Creative Commons, the Wikimedia Foundation and others had produced a proposal supported by both the FSF and Creative Commons to modify the Free Documentation License in such a fashion as to allow the possibility for the Wikimedia Foundation to migrate the projects to the similar Creative Commons Attribution Share-Alike (CC BY-SA) license. These changes were implemented on version 1.3 of the license, which includes a new provision allowing certain materials released under the license to be used under a Creative Commons Attribution Share-Alike license also.

Conditions.

Material licensed under the current version of the license can be used for any purpose, as long as the use meets certain conditions.

Secondary sections.

The license explicitly separates any kind of "Document" from "Secondary Sections", which may not be integrated with the Document, but exist as front-matter materials or appendices. Secondary sections can contain information regarding the author's or publisher's relationship to the subject matter, but not any subject matter itself. While the Document itself is wholly editable, and is essentially covered by a license equivalent to (but mutually incompatible with) the GNU General Public License, some of the secondary sections have various restrictions designed primarily to deal with proper attribution to previous authors.  Specifically, the authors of prior versions have to be acknowledged and certain "invariant sections" specified by the original author and dealing with his or her relationship to the subject matter may not be changed. If the material is modified, its title has to be changed (unless the prior authors give permission to retain the title).  The license also has provisions for the handling of front-cover and back-cover texts of books, as well as for "History", "Acknowledgements", "Dedications" and "Endorsements" sections. These features were added in part to make the license more financially attractive to commercial publishers of software documentation, some of whom were consulted during the drafting of the GFDL. "Endorsements" sections are intended to be used in official standard documents, where distribution of modified versions should only be permitted if they are not labeled as that standard any more.

Commercial redistribution.

The GFDL requires the ability to "copy and distribute the Document in any medium, either commercially or noncommercially" and therefore is incompatible with material that excludes commercial re-use. As mentioned above, the GFDL was designed with commercial publishers in mind, as Stallman explained: Material that restricts commercial re-use is incompatible with the license and cannot be incorporated into the work. However, incorporating such restricted material may be fair use under United States copyright law (or fair dealing in some other countries) and does not need to be licensed to fall within the GFDL if such fair use is covered by all potential subsequent uses. One example of such liberal and commercial fair use is parody.

Compatibility with Creative Commons licensing terms.

Although the two licenses work on similar copyleft principles, the GFDL is not compatible with the Creative Commons Attribution-ShareAlike license.  However, at the request of the Wikimedia Foundation, version 1.3 added a time-limited section allowing specific types of websites using the GFDL to additionally offer their work under the CC BY-SA license. These exemptions allow a GFDL-based collaborative project with multiple authors to transition to the CC BY-SA 3.0 license, without first obtaining the permission of every author, if the work satisfies several conditions:  To prevent the clause from being used as a general compatibility measure, the license itself only allowed the change to occur before August 1, 2009. At the release of version 1.3, the FSF stated that all content added before November 1, 2008 to Wikipedia as an example satisfied the conditions. The Wikimedia Foundation itself after a public referendum, invoked this process to dual-license content released under the GFDL under the CC BY-SA license in June 2009, and adopted a foundation-wide attribution policy for the use of content from Wikimedia Foundation projects.

Enforcement.

There have currently been no cases involving the GFDL in a court of law, although its sister license for software, the GNU General Public License, has been successfully enforced in such a setting. Although the content of Wikipedia has been plagiarized and used in violation of the GFDL by other sites, such as Baidu Baike, no contributors have ever tried to bring an organization to court due to violation of the GFDL. In the case of Baidu, Wikipedia representatives asked the site and its contributors to respect the terms of the licenses and to make proper attributions.

Criticism.

Some critics consider the GFDL a non-free license. Some reasons for this are that the GFDL allows "invariant" text which cannot be modified or removed, and that its prohibition against digital rights management (DRM) systems applies to valid usages, like for "private copies made and not distributed".  Notably, the Debian project, Thomas Bushnell, Nathanael Nerode, and Bruce Perens have raised objections. Bruce Perens saw the GFDL even outside the "Free Software ethos": In 2006, Debian developers voted to consider works licensed under the GFDL to comply with their Debian Free Software Guidelines provided the invariant section clauses are not used. The results was GFDL without invariant sections is DFSG compliant. However, their resolution stated that even without invariant sections, GFDL-licensed software documentation "is still not free of trouble", namely because of its incompatibility with the major free software licenses.  Those opposed to the GFDL have recommended the use of alternative licenses such as the BSD License or the GNU GPL.  The FLOSS Manuals foundation, an organization devoted to creating manuals for free software, decided to eschew the GFDL in favor of the GPL for its texts in 2007, citing the incompatibility between the two, difficulties in implementing the GFDL, and the fact that the GFDL "does not allow for easy duplication and modification", especially for digital documentation.

DRM clause.

The GNU FDL contains the statement:  A criticism of this language is that it is too broad, because it applies to private copies made but not distributed. This means that a licensee is not allowed to save document copies "made" in a proprietary file format or using encryption.  In 2003, Richard Stallman said about the above sentence on the debian-legal mailing list:

Invariant sections.

A GNU FDL work can quickly be encumbered because a new, different title must be given and a list of previous titles must be kept. This could lead to the situation where there are a whole series of title pages, and dedications, in each and every copy of the book if it has a long lineage. These pages cannot be removed until the work enters the public domain after copyright expires.  Richard Stallman said about invariant sections on the "debian-legal" mailing list:

GPL incompatible in both directions.

The GNU FDL is incompatible in both directions with the GPL—material under the GNU FDL cannot be put into GPL code and GPL code cannot be put into a GNU FDL manual. At the June 22nd and 23rd 2006 international GPLv3 conference in Barcelona, Eben Moglen hinted that a future version of the GPL could be made suitable for documentation:

Burdens when printing.

The GNU FDL requires that licensees, when printing a document covered by the license, must also include "this License, the copyright notices, and the license notice saying this License applies to the Document". This means that if a licensee prints out a copy of an article whose text is covered under the GNU FDL, they must also include a copyright notice and a physical printout of the GNU FDL, which is a significantly large document in itself. Worse, the same is required for the standalone use of just one (for example, Wikipedia) image. Wikivoyage, a web site dedicated to free content travel guides, chose not to use the GFDL because it considers it unsuitable for short printed texts.

Other free content licenses.

Some of these were developed independently of the GNU FDL, while others were developed in response to perceived flaws in the GNU FDL.

The GNU Free Documentation License (GNU FDL or simply GFDL) is a copyleft license for free documentation, designed by the Free Software Foundation (FSF) for the GNU Project. It is similar to the GNU General Public License, giving readers the rights to copy, redistribute, and modify (except for "invariant sections") a work and requires all copies and derivatives to be available under the same license. Copies may also be sold commercially, but, if produced in larger quantities (greater than 100), the original document or source code must be made available to the work's recipient.

La licence de documentation libre GNU (, abrégé en "GFDL") est une licence relevant du droit d'auteur produite par la. Elle a pour but de protéger la diffusion de contenu libre et peut être utilisée par chacun afin de déterminer le mode de diffusion de son œuvre.


Career.

In 1920 he met Max Delby, a teacher who helped him develop his career, and in April 1921 he flew as a pilot for the first time.

French Air Force.

Mermoz joined the French Air Force in 1922, being assigned, as a pilot of the air force's 11th regiment, to duty in Syria. In 1924, he returned to France, having arguably been one of the most successful pilots in the Syrian operations. Mermoz relocated to Toulouse.

Latécoère.

Mermoz went on to become an airmail pilot, with Latécoère's company, and almost failed his entry exam by performing dangerous stunts to impress the director. (The director, Didier Daurat had this famous quote: "We don't need acrobats here, we need bus drivers.") He then did a normal, flawless flight and was hired. It was there that Mermoz met Antoine de Saint-Exupéry. At the Compagnie Générale Aéropostale, Mermoz travelled to Morocco, Senegal and other African areas.  In 1926, one of Mermoz's flights ended with an accident, when his plane crashed in the Sahara. He was then taken hostage by a group of rebel Tuaregs, but was fortunately found later alive. In 1927, Latécoère began building his own brand of planes to replace the aging World War I aircraft Breguet 14. The Latécoère 25, (or "Laté 25") and, later, the Latécoère 26 and Latécoère 28 proved to be efficient aircraft when flying from Morocco to Senegal, and Mermoz himself flew the types on those routes on multiple occasions.  But Africa was only the beginning. Latécoère's project was to create a direct airline between France and South America. By 1929, it had become evident that it would be economically viable for France to establish a commercial air route to South America, so Mermoz and others flew over the Andes. Despite Mermoz finding the flying conditions over the Andes to be tough, he became the project's main pilot, determined to reach the Pacific Ocean, and he was able, after multiple stops, to reach Santiago, Chile. During that time, to save time, he decided to fly during the night, using light beacons and flares as guides; and his fellow pilots, for once, were a bit reluctant to see him do it, because they knew it would be their turn next. For some time, as transatlantic flights were not yet possible, steamboats linked both halves of the "Line". After flying from Saint-Louis, in Senegal, to Natal, Brazil, in 12–13 May 1930, the line was complete at last. Unfortunately, the modified Laté 28 "Comte-de-la-Vaulx" did not prove reliable enough, and had to ditch at sea during the return flight. Mermoz, his two companions and the mail were rescued, but the plane sank during the attempt to tow it.

Air France.

In 1933, Mermoz was appointed general inspector by Air France. That same year, he arrived in Buenos Aires, Argentina, where he and Saint-Exupéry became important persons during the infancy of Aeroposta Argentina, which would later become Aerolíneas Argentinas. Mermoz and Saint-Exupéry flew many dangerous flights for the then new air company. They became regarded as two of the most important men in the history of Argentine commercial aviation. From 1934 to 1936, Mermoz would fly private expeditions on Latécoère 300 airplanes. He flew 24 expeditions with that type. In 1935, he also flew de Havilland DH.88 "Comet" airplanes.

Disappearance at sea.

On 7 December 1936 he turned back shortly after take-off to report a troublesome engine on his Latécoère 300 "Croix-du-Sud" ("Southern Cross"). After learning that he would have to wait for another one to be prepared, he took off again in the same plane after a quick repair, concerned that he would be late in delivering the mail. (His last words before boarding the plane were "Quick, let's not waste time anymore.")  Four hours later, the radio station received a short message, where Mermoz reported that he had to cut the power on the aft starboard engine. The message was interrupted abruptly. No further messages were received, and neither the Laté 300 nor the crew were ever recovered.  It is assumed that the engine they had tried to repair lost its propeller midflight, and being one of the aft engines, the loose propeller either badly damaged or cut the hull entirely, causing the plane to lose its tail and crash instantly. Henri Guillaumet, one of Mermoz's fellow pilots, had encountered the same problem a few months before, but as his own engine was on the forward side, airspeed had been sufficient to maintain the propeller in place until the landing.

Sabotage of the "Southern Cross".

In 1941, the Investigative Commission of Anti-National Activities of the Parliament of Uruguay, after denunciations filed before the Deputy Tomas Brena and Julio Iturbide, arrives at the surprising conclusion of the last two airmail flights of Air France, and with result the death of Collenot first and Mermoz later, they were the result of sabotage of the Nazi Fifth Column (National German Socialist Workers Party operating in Uruguay). The air mail bags transported the technical and economic proposals for the bidding of the so-called Obra del Río Negro in Uruguay, the international tender carried out in three calls in 1936, for the construction of the Rincón del Bonete hydroelectric plant. The tender only receives Offers or proposals from the Siemens Bauunion and Philipp Holzmann AG consortium in Germany, and SKODA WORKS from Austria. This and other tricks, such as false news and bribes, were used by Nazi Germany, to get rid of the other proposals under way, and force the bidding to be declared void.  The crew of Latécoère 300 "Croix-du-Sud", F-AKGF, on that day were:

An unreliable plane.

Mermoz had grown dissatisfied with the quality of the planes he and his companions had to pilot. In the months before his demise, he had been vocal about the aircraft's poor quality in both design and material, and was quoted saying "Ask me to pilot anything, even a wheelbarrow, but at one condition: make sure it is "solid"". A similar plane, Laté 301 F-AOIK "Ville-de-Buenos-Aires", had disappeared eight months before his own, causing the death, among others, of his mechanic and friend Collenot. The complicated Hispano-Suiza 12Ner engines thought to be the cause of both crashes were later decommissioned and replaced with older, more reliable ones. His message had been heard too late.

Jean Mermoz (9 December 1901, Aubenton, Aisne – 7 December 1936) was a French aviator, viewed as a hero by other pilots such as Saint-Exupery, and in his native France, where many schools bear his name. In Brazil, he also is recognized as a pioneer aviator.

Jean Mermoz, né à Aubenton (Aisne) le et disparu dans l'océan Atlantique le, est un aviateur français, figure légendaire de l'Aéropostale, surnommé l'« Archange ».


Terminology.

Potash refers to potassium compounds and potassium-bearing materials, most commonly limited to potassium carbonate. The term "potash" comes from the Middle Dutch word "potaschen" ("pot ashes", 1477).  The old method of making potassium carbonate () was by collecting or producing wood ash (an occupation carried out by ash burners), leaching the ashes and then evaporating the resulting solution in large iron pots, leaving a white residue called "pot ash". Approximately 10% by weight of common wood ash can be recovered as pot ash. Later, "potash" became the term widely applied to naturally occurring potassium salts and the commercial product derived from them, although it most likely derived its name (where it was used) from the anion of the acid that replaced the carbonate moiety, a common equivocative use of "potash" for "potassium".  The following table lists a number of potassium compounds which use the word "potash" in their traditional names:

Production.

All commercial potash deposits come originally from evaporite deposits and are often buried deep below the earth's surface. Potash ores are typically rich in potassium chloride (KCl), sodium chloride (NaCl) and other salts and clays, and are typically obtained by conventional shaft mining with the extracted ore ground into a powder. Other methods include dissolution mining and evaporation methods from brines.  In the evaporation method, hot water is injected into the potash which is dissolved and then pumped to the surface where it is concentrated by solar induced evaporation. Amine reagents are then added to either the mined or evaporated solutions. The amine coats the KCl but not NaCl. Air bubbles cling to the amine + KCl and float it to the surface while the NaCl and clay sink to the bottom. The surface is skimmed for the amine + KCl which is then dried and packaged for use as a K rich fertilizer—KCl dissolves readily in water and is available quickly for plant nutrition.  Potash deposits can be found all over the world. At present, deposits are being mined in Canada, Russia, China, Belarus, Israel, Germany, Chile, the United States, Jordan, Spain, the United Kingdom, Uzbekistan and Brazil, with the most significant deposits present in Saskatchewan, Canada.

Occupational hazards.

Excessive respiratory disease has been a concern for potash miners throughout history due to environmental hazards, such as radon and asbestos. Potash miners are liable to develop silicosis. Based on a study done between 1977 and 1987, cardiovascular disease among potash workers, the overall mortality rates were low, but a noticeable difference in above-ground workers was documented.

History of production.

Potash (especially potassium carbonate) has been used in bleaching textiles, making glass, and making soap, since about AD 500. Potash was principally obtained by leaching the ashes of land and sea plants. Beginning in the 14th century potash was mined in Ethiopia. One of the world's largest deposits, 140 to 150 million tons, is located in the Tigray's Dallol area. Potash was one of the most important industrial chemicals. It was refined from the ashes of broadleaved trees and produced primarily in the forested areas of Europe, Russia, and North America. The first U.S. patent of any kind was issued in 1790 to Samuel Hopkins for an improvement "in the making of Pot ash and Pearl ash by a new Apparatus and Process". "Pearl ash" was a purer quality made by calcination of potash in a reverberatory furnace or kiln. Potash pits were once used in England to produce potash that was used in making soap for the preparation of wool for yarn production.  As early as 1767, potash from wood ashes was exported from Canada, and exports of potash and pearl ash reached 43,958 barrels in 1865. There were 519 asheries in operation in 1871. The industry declined in the late 19th century when large-scale production of potash from mineral salts was established in Germany. In 1943, potash was discovered in Saskatchewan, Canada, in the process of drilling for oil. Active exploration began in 1951. In 1958, the Potash Company of America became the first potash producer in Canada with the commissioning of an underground potash mine at Patience Lake; however, due to water seepage in its shaft, production stopped late in 1959 but following extensive grouting and repairs, resumed in 1965. The underground mine was flooded in 1987 and was reactivated for commercial production as a solution mine in 1989.  In the late 18th and early 19th centuries, potash production provided settlers in North America a way to obtain badly needed cash and credit as they cleared wooded land for crops. To make full use of their land, settlers needed to dispose of excess wood. The easiest way to accomplish this was to burn any wood not needed for fuel or construction. Ashes from hardwood trees could then be used to make lye, which could either be used to make soap or boiled down to produce valuable potash. Hardwood could generate ashes at the rate of 60 to 100 bushels per acre (500 to 900 m3/km2). In 1790, ashes could be sold for $3.25 to $6.25 per acre ($800 to $1,500/km2) in rural New York State – nearly the same rate as hiring a laborer to clear the same area. Potash making became a major industry in British North America. Great Britain was always the most important market. The American potash industry followed the woodsman's ax across the country. After about 1820, New York replaced New England as the most important source; by 1840 the center was in Ohio. Potash production was always a by-product industry, following from the need to clear land for agriculture. In 1964 a Canadian company known as Kalium Chemicals established the first potash mine that took advantage of the solution process. The discovery was made during oil reserve exploration. The mine was developed near Regina, Saskatchewan. The mine reached depths greater than 1500 meters. Mosaic's, Belle Plaine had later gone to undertake the operation of the mine. Most of the world reserves of potassium (K) were deposited as sea water in ancient inland oceans. After the water evaporated, the potassium salts crystallized into beds of potash ore. These are the locations where potash is being mined today. The deposits are a naturally occurring mixture of potassium chloride (KCl) and sodium chloride (NaCl), more commonly known as table salt. Over time, as the surface of the earth changed, these deposits were covered by thousands of feet of earth.  Most potash mines today are deep shaft mines as much as 4,400 feet (1,400 m) underground. Others are mined as strip mines, having been laid down in horizontal layers as sedimentary rock. In above-ground processing plants, the KCl is separated from the mixture to produce a high-analysis potassium fertilizer. Other potassium salts can be separated by various procedures, resulting in potassium sulfate and potassium-magnesium sulfate.  Today some of the world's largest known potash deposits are spread all over the world from Saskatchewan, Canada, to Brazil, Belarus, Germany, and the Permian Basin. The Permian basin deposit includes the major mines outside of Carlsbad, New Mexico, to the world's purest potash deposit in Lea County, New Mexico (not far from the Carlsbad deposits), which is believed to be roughly 80% pure. (Osceola County, Michigan has deposits 90+% pure; however, the only mine there was converted to salt production.) Canada is the largest producer, followed by Russia and Belarus. The most significant reserve of Canada's potash is located in the province of Saskatchewan and is mined by The Mosaic Company, Nutrien and K+S.  In China, most potash deposits are concentrated in the deserts and salt flats of the endorheic basins of its western provinces, particularly Qinghai. Geological expeditions discovered the reserves in the 1950s but commercial exploitation lagged until Deng Xiaoping's Reform and Opening Up Policy in the 1980s. The 1989 opening of the Qinghai Potash Fertilizer Factory in the remote Qarhan Playa increased China's production of potassium chloride sixfold, from less than a year at Haixi and Tanggu to just under a year.  In the beginning of the 20th century, potash deposits were found in the Dallol Depression in Musely and Crescent localities near the Ethiopean-Eritrean border. The estimated reserves are 173 and 12 million tonnes for the Musely and Crescent, respectively. The latter is particularly suitable for surface mining; it was explored in the 1960s but the works stopped due to the flood in 1967. Attempts to continue mining in the 1990s were halted by the Eritrean–Ethiopian War and have not resumed as of 2009.  Recovery of potassium fertilizer salts from sea water has been studied in India. During extraction of salt from seawater by evaporation, potassium salts get concentrated in bittern, an effluent from the salt industry.  In 2013, almost 70% of potash production was controlled by Canpotex, an exporting and marketing firm, and the Belarusian Potash Company. The latter was a joint venture between Belaruskali and Uralkali, but on July 30, 2013, Uralkali announced that it had ended the venture.

Consumption.

Fertilizers.

Potassium is the third major plant and crop nutrient after nitrogen and phosphorus. It has been used since antiquity as a soil fertilizer (about 90% of current use). Elemental potassium does not occur in nature because it reacts violently with water. As part of various compounds, potassium makes up about 2.6% of the Earth's crust by mass and is the seventh most abundant element, similar in abundance to sodium at approximately 1.8% of the crust. Potash is important for agriculture because it improves water retention, yield, nutrient value, taste, color, texture and disease resistance of food crops. It has wide application to fruit and vegetables, rice, wheat and other grains, sugar, corn, soybeans, palm oil and cotton, all of which benefit from the nutrient's quality-enhancing properties.  Demand for food and animal feed has been on the rise since 2000. The United States Department of Agriculture's Economic Research Service (ERS) attributes the trend to average annual population increases of 75 million people around the world. Geographically, economic growth in Asia and Latin America greatly contributed to the increased use of potash-based fertilizer. Rising incomes in developing countries also was a factor in the growing potash and fertilizer use. With more money in the household budget, consumers added more meat and dairy products to their diets. This shift in eating patterns required more acres to be planted, more fertilizer to be applied and more animals to be fed—all requiring more potash.  After years of trending upward, fertilizer use slowed in 2008. The worldwide economic downturn is the primary reason for the declining fertilizer use, dropping prices, and mounting inventories.  The world's largest consumers of potash are China, the United States, Brazil, and India. Brazil imports 90% of the potash it needs. Potash consumption for fertilizers is expected to increase to about 37.8 million tonnes by 2022.  Potash imports and exports are often reported in KO "equivalent", although fertilizer never contains potassium oxide, per se, because potassium oxide is caustic and hygroscopic.

Pricing.

At the beginning of 2008, potash prices started a meteoric climb from less than US$200 a tonne to a high of US$875 in February 2009. These subsequently dropped dramatically to an April 2010 low of US$310 level, before recovering in 2011–12, and relapsing again in 2013. For reference, prices in November 2011 were about US$470 per tonne, but as of May 2013 were stable at US$393. After the surprise breakup of the world's largest potash cartel at the end of July 2013, potash prices were poised to drop some 20 percent. At the end of Dec 2015, potash traded for US$295 a tonne. In April 2016 its price was US$269. In May 2017, prices had stabilised at around US$216 a tonne down 18% from the previous year. By January 2018, prices have been recovering to around US$225 a tonne. World potash demand tends to be price inelastic in the short-run and even in the long run.

Other uses.

In addition to its use as a fertilizer, potassium chloride is important in many industrialized economies, where it is used in aluminium recycling, by the chloralkali industry to produce potassium hydroxide, in metal electroplating, oil-well drilling fluid, snow and ice melting, steel heat-treating, in medicine as a treatment for hypokalemia, and water softening. Potassium hydroxide is used for industrial water treatment and is the precursor of potassium carbonate, several forms of potassium phosphate, many other potassic chemicals, and soap manufacturing. Potassium carbonate is used to produce animal feed supplements, cement, fire extinguishers, food products, photographic chemicals, and textiles. It is also used in brewing beer, pharmaceutical preparations, and as a catalyst for synthetic rubber manufacturing. Also combined with silica sand to produce potassium silicate, sometimes known as waterglass, for use in paints and arc welding electrodes. These non-fertilizer uses have accounted for about 15% of annual potash consumption in the United States.

Substitutes.

No substitutes exist for potassium as an essential plant nutrient and as an essential nutritional requirement for animals and humans. Manure and glauconite (greensand) are low-potassium-content sources that can be profitably transported only short distances to crop fields.

Potash () includes various mined and manufactured salts that contain potassium in water-soluble form. The name derives from "pot ash", which refers to plant ashes soaked in water in a pot, the primary means of manufacturing the product before the industrial era. The word "potassium" is derived from potash.

La potasse désigne communément un minerai salin dit de roches évaporitiques, à base de chlorure de potassium, utilisé comme point de départ des principaux dérivés potassiques ainsi que dans l'industrie des engrais. On peut aussi l'extraire en grande quantité des eaux de la mer.


History.

Origins.

The genre that is recognized today as "real-time strategy" emerged as a result of an extended period of evolution and refinement. Games that are today sometimes perceived as ancestors of the real-time strategy genre were never marketed or designed as such at the original date of publication. As a result, designating "early real-time strategy" titles is problematic because such games are being held up to modern standards. The genre initially evolved separately in the United Kingdom, Japan, and North America, afterward gradually merging into a unified worldwide tradition.  Tim Barry in May 1981 described in "InfoWorld" a multiplayer, real-time strategy space game that ran ("and probably still is") on an IBM System/370 Model 168 at a large San Francisco Bay area company. He stated that it had "far better support than many of the application programs used in the business", with a published manual and regular schedule. Comparing its complexity to "Dallas", Barry recalled that "when the game was restored at 5 P.M., a lot of regular work stopped".  Ars Technica traces the genre's roots back to "Utopia" (1981), citing it as the "birth of a genre", with a "real-time element" that was "virtually unheard of", thus making it "arguably the earliest ancestor of the real-time strategy genre". According to Ars Technica, "Utopia" was a turn-based strategy game with hybrid elements that ran "in real-time but events happened on a regular turn-based cycle." According to Brett Weiss, "Utopia" is often cited as "the first real-time strategy game." According to Matt Barton and Bill Loguidice, "Utopia" "helped set the template" for the genre, but has "more in common with "SimCity" than it does with "Dune II" and later RTS games." Allgame listed "War of Nerves" as the oldest "2D Real-Time Strategy". Barton also cites "Cytron Masters" (1982), saying it was "one of the first (if not "the" first) real-time strategy games." On the other hand, Scott Sharkey of 1UP argues that, while "Cytron Masters" "attempted real time strategy", it was "much more tactical than strategic" due to "the inability to construct units or manage resources". "BYTE" in December 1982 published as an Apple II type-in program "Cosmic Conquest". The winner of the magazine's annual Game Contest, the author described it as a "single-player game of real-time action and strategic decision making". The magazine described it as "a real-time space strategy game". The game has elements of resource management and wargaming.  In the United Kingdom, the earliest real-time strategy games are "Stonkers" by John Gibson, published in 1983 by Imagine Software for the ZX Spectrum, and "Nether Earth" for ZX Spectrum in 1987. In North America, the oldest game retrospectively classified as real-time strategy by several sources is "The Ancient Art of War" (1984), designed by Evryware's Dave and Barry Murry, followed by "The Ancient Art of War at Sea" in 1987.  In Japan, the earliest is "Bokosuka Wars" (1983), an early strategy RPG (or "simulation RPG"); the game revolves around the player leading an army across a battlefield against enemy forces in real-time while recruiting/spawning soldiers along the way, for which it is considered by Ray Barnholt of 1UP.com to be an early prototype real-time strategy game. Another early title with real-time strategy elements is Sega's "Gain Ground" (1988), a strategy-action game that involved directing a set of troops across various enemy-filled levels. TechnoSoft's "Herzog" (1988) is regarded as a precursor to the real-time strategy genre, being the predecessor to "Herzog Zwei" and somewhat similar in nature, though primitive in comparison.  IGN cites "Herzog Zwei", released for the Sega Mega Drive/Genesis home console in 1989 as "arguably the first RTS game ever", and it is often cited as "the first real-time strategy game" according to "Ars Technica". It combines traditional strategy gameplay with fully real-time, fast-paced, arcade-style action gameplay, featuring a split-screen two-player mode where both players are in action simultaneously and there are no pauses while decisions are taken, forcing players to think quickly while on the move. In "Herzog Zwei", though the player only controls one unit, the manner of control foreshadowed the point-and-click mechanic of later games. Scott Sharkey of 1UP argues that it introduced much of the genre conventions, including unit construction and resource management, with the control and destruction of bases being an important aspect of the game, as were the economic/production aspects of those bases. "Herzog Zwei" is credited by 1UP as a landmark that defined the genre and as "the progenitor of all modern real-time strategy games." Chuck Sperry cited "Herzog Zwei" as an influence on "Dune II".  Notable as well are early games like "Mega Lo Mania" by Sensible Software (1991) and "Supremacy" (also called "Overlord" – 1990). Although these two lacked direct control of military units, they both offered considerable control of resource management and economic systems. In addition, "Mega Lo Mania" has advanced technology trees that determine offensive and defensive prowess. Another early (1988) game, "Carrier Command" by Realtime Games, involved real-time responses to events in the game, requiring management of resources and control of vehicles. The early game "Sim Ant" by Maxis (1991) had resource gathering, and controlling an attacking army by having them follow a lead unit. However, it was with the release of "Dune II" from Westwood Studios (1992) that real-time strategy became recognized as a distinct genre of video games.

1992–1998: seminal titles.

Although real-time strategy games have an extensive history, some titles have served to define the popular perception of the genre and expectations of real-time strategy titles more than others, in particular the games released between 1992 and 1998 by Westwood Studios and Blizzard Entertainment.  Drawing influence from "Herzog Zwei", "Populous", "Eye of the Beholder", and the Macintosh user interface, Westwood's "Dune II: The Building of a Dynasty" (1992) featured all the core concepts and mechanics of modern real-time strategy games that are still used today, such as using the mouse to move units, and gathering resources, and as such served as the prototype for later real-time strategy games. According to its co-designer and lead programmer, Joe Bostic, a "benefit over "Herzog Zwei" is that we had the advantage of a mouse and keyboard. This greatly facilitated precise player control, which enabled the player to give orders to individual units. The mouse, and the direct control it allowed, was critical in making the RTS genre possible.”  The success of "Dune II" encouraged several games which became influential in their own right." " (1994) achieved great prominence upon its release, owing in part to its use of a fantasy setting and also to its depiction of a wide variety of buildings (such as farms) which approximated a full fictitious society, not just a military force. "Command & Conquer", as well as "", became the most popular early RTS games. These two games contended with "" after its release in late 1995.  "Total Annihilation", released by Cavedog Entertainment in 1997, introduced 3D units and terrain and focused on huge battles that emphasized macromanagement over micromanagement. It featured a streamlined interface that would influence many RTS games in later years. "Age of Empires", released by Ensemble Studios in 1997 tried to put a game in a slower pace, combining elements of "Civilization" with the real-time strategy concept by introducing ages of technologies. In 1998, Blizzard released the game "StarCraft", which became an international phenomenon and is still played in large professional leagues to this day. Collectively, all of these games defined the genre, providing the "de facto" benchmark against which new real-time strategy games are measured.

Refinement and transition to 3D.

The real-time strategy genre has been relatively stable since 1995. Additions to the genre's concept in newer games tend to emphasize more of the basic RTS elements (higher unit caps, more unit types, larger maps, etc.). Rather than innovations to the game concept, new games generally focus on refining aspects of successful predecessors. As the paragon example of gameplay refinement, Cavedog's acclaimed "Total Annihilation" from 1997 distilled the core mechanics of "Command & Conquer", and introduced the first 3D units and terrain in real-time strategy games. The "Age of Empires" focus on historical setting and age advancement was refined further by its sequel, "Age of Empires II: Age of Kings", and by Stainless Steel Studios' "Empire Earth" in 2001. GSC Game World's "" series took the genre in a different direction, bringing population caps into the tens of thousands.  "Dungeon Keeper" (1997), "" (1998), "Jeff Wayne's The War of the Worlds" (1998), "Warzone 2100" (1999), "Machines" (1999), "Homeworld" (1999), "Honour & Freedom" (1999), and "Dark Reign 2" (2000) were among the first completely 3D real-time strategy titles. "Homeworld" was notable in that it featured a 3D environment in space, therefore allowing movement in every direction, a feature which its semi-sequel, "Homeworld Cataclysm" (2000) continued to build upon adding features such as waypoints. "Homeworld 2", released in 2003, streamlined movement in the 360° 3D environment. Furthermore, "Machines", which was also released in 1999 and featured a nearly 100% 3D environment, attempted to combine the RTS genre with a first-person shooter (FPS) genre although it was not a particularly successful title. These games were followed by a short period of interest in experimental strategy games such as "Allegiance" (2000). "Jeff Wayne's The War of the Worlds" was notable for being one of the few completely non-linear RTS games ever.  It is only in approximately 2002 that 3D real-time strategy became the standard, with both "Warcraft III" (2002) and Ensemble Studio's "Age of Mythology" (2002) being built on a full 3D game engine. "" introduced classic wargame elements, such as supply lines to the genre. "Battle Realms" (2001) was another full 3D game, but had limited camera views.  The move from 2D to 3D has been criticized in some cases. Issues with controlling the camera and placement of objects have been cited as problems.

Specialization and evolution.

A few games have experimented with diversifying map design, which continues to be largely two-dimensional even in 3D engines. "Earth 2150" (2000) allowed units to tunnel underground, effectively creating a dual-layer map; three-layer (orbit-surface-underground) maps were introduced in "Metal Fatigue". In addition, units could even be transported to entirely separate maps, with each map having its own window in the user interface. "" (2001) offered a simpler model: the main map contains locations that expand into their own maps. In these examples, however, the gameplay was essentially identical regardless of the map layer in question. "" (2005) emphasized its dual-layer maps by placing one of the game's two main resources in each map, making exploration and control of both maps fundamentally valuable.  Relatively few genres have emerged from or in competition with real-time strategy games, although real-time tactics (RTT), a superficially similar genre, emerged around 1995. In 1998, Activision attempted to combine the real-time strategy and first-person shooter genres in "Battlezone" (1998), while in 2002 Rage Games Limited attempted this with the "Hostile Waters" games. Later variants have included "Natural Selection" (2002), a game modification based on the Half-Life engine, and the free software "Tremulous"/"Unvanquished". "" (2003) combined the RPG and RTS elements in an online game.  Some games, borrowing from the real-time tactics (RTT) template, have moved toward an increased focus on tactics while downplaying traditional resource management, in which designated units collect the resources used for producing further units or buildings. Titles like "" (2004), "" (2006), and "Company of Heroes" (2006) replace the traditional resource gathering model with a strategic control-point system, in which control over strategic points yields construction/reinforcement points. "Ground Control" (2000) was the first such game to replace individual units with "squads".  Others are moving away from the traditional real-time strategy game model with the addition of other genre elements. One example is "Sins of a Solar Empire" (2008), released by Ironclad Games, which mixes elements of grand-scale stellar empire building games like "Master of Orion" with real-time strategy elements. Another example is indie game "Achron" (2011), which incorporates time travel as a game mechanic, allowing a player to send units forward or backward in time.  Multiplayer online battle arena games (MOBA) have originated as a subgenre of real-time strategy games, however this fusion of real-time strategy, role-playing, and action games has lost many traditional RTS elements. These type of games moved away from constructing additional structures, base management, army building, and controlling additional units. Map and the main structures for each team are still present, and destroying enemy main structure will secure victory as the ultimate victory condition. Unlike in RTS, a player has control over the only one single powerful unit, called "hero" or "champion", who advances in level, learns new abilities, and grows in power over the course of a match. Players can find various friendly and enemy units on the map at any given time assisting each team, however, these units are computer-controlled and players usually don't have direct control over their movement and creation; instead, they march forward along set paths. "Defense of the Ancients" ("DotA"), a "" mod from 2003, and its standalone sequel "Dota 2" (2013), as well as "League of Legends" (2009), and "Heroes of the Storm" (2015), are the typical representatives of the new strategy subgenre.

Gameplay.

In a typical real-time strategy game, the screen is divided into a map area displaying the game world and terrain, units, and buildings, and an interface overlay containing command and production controls and often a "radar" or "minimap" overview of the entire map. The player is usually given an isometric perspective of the world, or a free-roaming camera from an aerial viewpoint for modern 3D games. Players mainly scroll the screen and issue commands with the mouse, and may also use keyboard shortcuts.  Gameplay generally consists of the player being positioned somewhere in the map with a few units or a building that is capable of building other units/buildings. Often, but not always, the player must build specific structures to unlock more advanced units in the tech tree. Often, but not always, RTS games require the player to build an army (ranging from small squads of no more than 2 units, to literally hundreds of units) and using them to either defend themselves from a virtual form of Human wave attack or to eliminate enemies who possess bases with unit production capacities of their own. Occasionally, RTS games will have a preset number of units for the player to control and do not allow building of additional ones.  Resource gathering is commonly the main focus of the RTS games, but other titles of the genre place higher gameplay significance to how units are used in combat ("" for example, awards credits for territory captured rather than gathered resources), the extreme example of which are games of the real-time tactical genre. Some titles impose a ceiling on the number simultaneous troops, which becomes a key gameplay consideration, a significant example being "StarCraft", while other titles have no such unit cap.

Micromanagement and macromanagement.

Micromanagement deals with a player's constant need to manage and maintain individual units and resources on a fine scale. On the other hand, macromanagement refers to a player's management of economic expansion and large-scale strategic maneuvering, allowing the player time to think and consider possible solutions. Micromanagement involves the use of combat tactics involved in the present, whereas macromanagement considers the greater scale of the game in an attempt to predict the future.

Criticism of gameplay.

Because of their generally faster-paced nature (and in some cases a smaller learning curve), real-time strategy games have surpassed the popularity of turn-based strategy computer games. In the past, a common criticism was to regard real-time strategy games as "cheap imitations" of turn-based strategy games, arguing that real-time strategy games had a tendency to devolve into "click-fests" in which the player who was faster with the mouse generally won, because they could give orders to their units at a faster rate. The common retort is that success involves not just fast clicking, but also the ability to make sound decisions under time pressure. The "clickfest" argument is also often voiced alongside a "button babysitting" criticism, which pointed out that a great deal of game time is spent either waiting and watching for the next time a production button could be clicked, or rapidly alternating between different units and buildings, clicking their respective button.  A third common criticism is that real-time gameplay often degenerates into "rushes" where the players try to gain the advantage and subsequently defeat the opponent as quickly in the game as possible, preferably before the opposition is capable of successfully reacting. For example, the original "Command & Conquer" gave birth to the now-common "tank rush" tactic, where the game outcome is often decided very early on by one player gaining an initial advantage in resources and producing large amounts of a relatively powerful but still quite cheap unit—which is thrown at the opposition before they have had time to establish defenses or production. Although this strategy has been criticized for encouraging overwhelming force over strategy and tactics, defenders of the strategy argue that they're simply taking advantage of the strategies utilized, and some argue that it is a realistic representation of warfare. One of the most infamous versions of a rush is the "Zergling rush" from the real-time strategy game "StarCraft", where the Zerg player would morph one of their starting workers (or the first one produced) into a spawning pool immediately and use all of their resources to produce Zerglings, attacking once they have enough to overwhelm any early defense; in fact, the term "zerging" has become synonymous with rushing.  A fourth criticism of the RTS genre is the importance of skill over strategy in real-time strategy games. The manual dexterity and ability to multitask and divide one's attention is often considered the most important aspect to succeeding at the RTS genre. According to Troy Dunniway, former Westwood developer who has also worked on "", "A player controls hundreds of units, dozens of buildings and many different events that are all happening simultaneously. There is only one player, and he can only pay attention to one thing at a time. Expert players can quickly flip between many different tasks, while casual gamers have more problems with this."

Tactics vs. strategy.

Real-time strategy games have been criticized for an overabundance of tactical considerations when compared to the amount of strategic gameplay found in such games. According to Chris Taylor, lead designer of "Supreme Commander", he said, "[My first attempt at visualizing RTSs in a fresh and interesting new way] was my realizing that although we call this genre 'Real-Time Strategy,' it should have been called 'Real-Time Tactics' with a dash of strategy thrown in." (Taylor then posits his own game as having surpassed this mold by including additional elements of broader strategic scope.)  In general terms, military strategy refers to the use of a broad arsenal of weapons including diplomatic, informational, military, and economic resources, whereas military tactics is more concerned with short-term goals such as winning an individual battle. In the context of strategy video games, however, the difference is often reduced to the more limited criteria of either a presence or absence of base building and unit production.  In an article for Gamasutra, Nathan Toronto criticizes real-time strategy games for too often having only one valid means of victory — attrition — comparing them unfavorably to real-time tactics games. Players' awareness that the only way for them to win or lose is militarily makes them unlikely to respond to gestures of diplomacy. The result is that the winner of a real-time strategy game is too often the best tactician rather than the best strategist. Troy Goodfellow counters this by saying that the problem is not that real-time strategy games are lacking in strategy (he says attrition is a form of strategy), rather it is that they too often have the "same" strategy: produce faster than you consume. He also states that building and managing armies is the conventional definition of real-time strategy, and that it is unfair to make comparisons with other genres.  In an article for GameSpy, Mark Walker criticizes real-time strategy games for their "lack" of combat tactics, suggesting real-time tactics games as a more suitable substitute. He also says that developers need to begin looking outside the genre for new ideas in order for strategy games to continue to be successful in the future.

Turn-based vs. real-time.

A debate has emerged between fans of real-time strategy (RTS) and turn-based strategy (TBS) (and related genres) based on the merits of the real-time and turn-based systems. Some titles attempt to merge the two systems: for example, the role-playing game "Fallout" uses turn-based combat and real-time gameplay, while the real-time strategy games "Homeworld", "Rise of Nations", and the games of the "Total War" series allow the player to pause the game and issue orders. Additionally, the "Total War" series has a combination of a turn-based strategy map with a real-time battle map. Another example of a game combining both turn-based game and real-time-strategy is "" which allows players, in a 'War of the Ring' game, to play a turn-based strategy game, but also battle each other in real time.

On consoles.

Despite "Herzog Zwei", a console game, laying the foundations for the real-time strategy genre, RTS games never gained popularity on consoles like they did on the PC platform. Real-time strategy games made for video game consoles have been consistently criticized due to their control schemes, as the PC's keyboard and mouse are considered to be superior to a console's gamepad for the genre. Thus, RTS games for home consoles have been met with mixed success. Scott Sharkey of 1UP notes that "Herzog Zwei" had already "offered a nearly perfect solution to the problem by giving the player direct control of a single powerful unit and near autonomy for everything else," and is surprised "that more console RTS games aren't designed with this kind of interface in mind from the ground up, rather than imitating" PC control schemes "that just doesn't work very well with a controller". Some handheld consoles like "Napoleon" on the GBA uses a similar solution.  However, "Halo Wars", which was released in 2009 for the Xbox 360, generated generally positive reviews, achieved an 82% critic average on aggregate web sites, and sold over 1 million copies. According to IGN, the gameplay lacks the traditional RTS concepts of limited resources and resource gathering and lacks multiple buildings.

Graphics.

"Total Annihilation" (1997) was the first real-time strategy game to utilize true 3D units, terrain, and physics in both rendering and in gameplay. For instance, the missiles in "Total Annihilation" travel in real time in simulated 3D space, and they can miss their target by passing over or under it. Similarly, missile-armed units in "Earth 2150" are at a serious disadvantage when the opponent is on high ground because the missiles often hit the cliffside, even in the case when the attacker is a missile-armed helicopter. "Homeworld", "Warzone 2100 and Machines" (all released in 1999) advanced the use of fully 3D environments in real-time strategy titles. In the case of "Homeworld", the game is set in space, offering a uniquely exploitable 3D environment in which all units can move vertically in addition to the horizontal plane. However, the near-industry-wide switch to full 3D was very gradual and most real-time strategy titles, including the first sequels to "Command & Conquer", initially used isometric 3D graphics made by pre-rendered 3D tiles. Only in later years did these games begin to use true 3D graphics and gameplay, making it possible to rotate the view of the battlefield in real-time. "Spring" is a good example of the transformation from semi-3D to full-3D game simulations. It is an "open-source" project which aims to give a "Total Annihilation" game-play experience in three dimensions. The most ambitious use of full 3D graphics was realized in "Supreme Commander", where all projectiles, units and terrain were simulated in real time, taking full advantage of the UI's zoom feature, which allowed cartographic style navigation of the 3D environment. This led to a number of unique gameplay elements, which were mostly obscured by the lack of computing power available in 2007, at the release date.  Japanese game developers Nippon Ichi and Vanillaware worked together on "Grim Grimoire", a PlayStation 2 title released in 2007, which features hand-drawn animated 2D graphics.  From 2010, real-time strategy games more commonly incorporated physics engines, such as Havok, in order to increase realism experienced in gameplay. A modern real-time strategy game that uses a physics engine is Ensemble Studios' "Age of Empires III", released on October 18, 2005, which used the Havok Game Dynamics SDK to power its real-time physics. "Company of Heroes" is another real-time strategy game that uses realistically modeled physics as a part of gameplay, including fully destructible environments.

Tournaments.

RTS World tournaments have been held for both "StarCraft" and "Warcraft III" since their 1998 and 2002 releases. The games have been so successful that some players have earned over $200,000 at the "Warcraft III World Championships". In addition, hundreds of "" tournaments are held yearly, as it is becoming an increasingly popular branch of e-sports. Notable tournaments include MLG, GSL, and Dreamhack. RTS tournaments are especially popular in South Korea.

Real-time strategy (RTS) is a sub-genre of strategy video games in which the game does not progress incrementally in turns, as is the case for turn-based strategy (TBS) games, where all players take turns while playing. The term "real-time strategy" was coined by Brett Sperry to market "Dune II" in the early 1990s.

Le jeu de stratégie en temps réel (STR ou RTS pour la dénomination du genre en anglais : ) est un type de jeu vidéo de stratégie particulier qui notamment et par opposition au jeu de stratégie au tour par tour n’utilise pas un découpage arbitraire du temps en tours de jeu.


History.

Since 1760 Swiss naturalist Horace-Bénédict de Saussure began to go to Chamonix to observe Mont Blanc. He tried with the Courmayeur mountain guide Jean-Laurent Jordaney, native of Pré-Saint-Didier, who accompanied De Saussure since 1774 on the Miage Glacier and on mont Crammont.  The first recorded ascent of Mont Blanc (at the time neither within Italy nor France) was on 8 August 1786 by Jacques Balmat and the doctor Michel Paccard. This climb, initiated by Horace-Bénédict de Saussure, who gave a reward for the successful ascent, traditionally marks the start of modern mountaineering. The first woman to reach the summit was Marie Paradis in 1808.  Nowadays the summit is ascended by an average of 20,000 mountaineer-tourists each year. It could be considered a technically easy, yet arduous, ascent for someone who is well-trained and acclimatized to the altitude. From l'Aiguille du Midi (where the cable car stops), Mont Blanc seems quite close, being higher. But while the peak seems deceptively close, La Voie des 3 Monts route (known to be more technical and challenging than other more commonly used routes) requires much ascent over two other 4,000 m mountains, Mont Blanc du Tacul and Mont Maudit, before the final section of the climb is reached and the last 1,000 m push to the summit is undertaken.  Each year climbing deaths occur on Mont Blanc, and on the busiest weekends, normally around August, the local rescue service performs an average of 12 missions, mostly directed to aid people in trouble on one of the normal routes of the mountain. Some routes require knowledge of high-altitude mountaineering, a guide (or at least an experienced mountaineer), and all require proper equipment. All routes are long and arduous, involving delicate passages and the hazard of rock-fall or avalanche. Climbers may also suffer altitude sickness, occasionally life threatening, particularly if they do not acclimatize to it.

Ownership of the summit.

The border between Italy and France passes through the summit of Mont Blanc, making it both French and Italian.  Since the French Revolution, the issue of the ownership of the summit has been debated. From 1416 to 1792, the entire mountain was within the Duchy of Savoy. In 1723, the Duke of Savoy, Victor Amadeus II, acquired the Kingdom of Sardinia. The resulting state of Sardinia was to become preeminent in the Italian unification. In September 1792, the French revolutionary Army of the Alps under Anne-Pierre de Montesquiou-Fézensac seized Savoy without much resistance and created a department of the Mont-Blanc. In a treaty of 15 May 1796, Victor Amadeus III of Sardinia was forced to cede Savoy and Nice to France. In article 4 of this treaty it says: "The border between the Sardinian kingdom and the departments of the French Republic will be established on a line determined by the most advanced points on the Piedmont side, of the summits, peaks of mountains and other locations subsequently mentioned, as well as the intermediary peaks, knowing: starting from the point where the borders of Faucigny, the Duchy of Aoust and the Valais, to the extremity of the glaciers or Monts-Maudits: first the peaks or plateaus of the Alps, to the rising edge of the Col-Mayor". This act further states that the border should be visible from the town of Chamonix and Courmayeur. However, neither is the peak of the Mont Blanc visible from Courmayeur nor is the peak of the Mont Blanc de Courmayeur visible from Chamonix because part of the mountains lower down obscure them. After the Napoleonic Wars, the Congress of Vienna restored the King of Sardinia in Savoy, Nice and Piedmont, his traditional territories, overruling the 1796 Treaty of Paris. Forty-five years later, after the Second Italian War of Independence, it was replaced by a new legal act. This act was signed in Turin on 24 March 1860 by Napoleon III and Victor Emmanuel II of Savoy, and deals with the annexation of Savoy (following the French neutrality for the plebiscites held in Tuscany, Modena, Parma and Romagna to join the Kingdom of Sardinia, against the Pope's will). A demarcation agreement, signed on 7 March 1861, defined the new border. With the formation of Italy, for the first time Mont Blanc was located on the border of France and Italy.  The 1860 act and attached maps are still legally valid for both the French and Italian governments. One of the prints from the 1823 "Sarde Atlas" positions the border exactly on the summit edge of the mountain (and measures it to be high). The convention of 7 March 1861 recognises this through an attached map, taking into consideration the limits of the massif, and drawing the border on the icecap of Mont Blanc, making it both French and Italian. Watershed analysis of modern topographic mapping not only places the main summit on the border, but also suggests that the border should follow a line northwards from the main summit towards Mont Maudit, leaving the southeast ridge to Mont Blanc de Courmayeur wholly within Italy.  Although the Franco-Italian border was redefined in both 1947 and 1963, the commission made up of both Italians and French ignored the Mont Blanc issue. The area from the Torino Hut to the summit is under the control of the Italian authority. NATO uses Italian military maps to operate. In the early 21st century, administration of the mountain is shared between the Italian town of Courmayeur and the French town of Saint-Gervais-les-Bains, although the larger part of the mountain lies within the commune of the latter.  In 2015, press reports suggested that claims by Italian mountaineers and cartographers on the disputed territory were still ongoing. As of 2020, the Swiss National Map, which covers the massif at 1:50'000 scale, shows both disputed areas around Mont Blanc and Dôme du Goûter in a neutral way, after previously following the French interpretation of the border until 2018.

Vallot.

The first professional scientific investigations on the summit were conducted by the botanist–meteorologist Joseph Vallot at the end of the 19th century. He wanted to stay near the top of the summit, so he built his own permanent cabin.

Janssen observatory.

In 1890, Pierre Janssen, an astronomer and the director of the Meudon astrophysical observatory, considered the construction of an observatory at the summit of Mont Blanc. Gustave Eiffel agreed to take on the project, provided he could build on a rock foundation, if found at a depth of less than below the ice. In 1891, the Swiss surveyor Imfeld dug two horizontal tunnels 12 m below the ice summit but found nothing solid. Consequently, the Eiffel project was abandoned.  Despite this, the observatory was built in 1893. During the cold wave of January 1893, a temperature of was recorded on Mont Blanc, being the lowest ever recorded there.  Levers attached to the ice supported the observatory. This worked to some extent until 1906, when the building started leaning heavily. The movement of the levers corrected the lean slightly, but three years later (two years after Janssen's death), a crevasse started opening under the observatory. It was abandoned. Eventually the building fell, and only the tower could be saved "in extremis".

Air crashes.

The mountain was the scene of two fatal air crashes; Air India Flight 245 in 1950 and Air India Flight 101 in 1966. Both planes were approaching Geneva Airport and the pilots miscalculated their descent; 48 and 117 people, respectively, died. The latter passengers included nuclear scientist Homi J. Bhabha, known as the "father" of India's nuclear programme.

Tunnel.

In 1946, a drilling project was initiated to carve a tunnel through the mountain. The Mont Blanc tunnel would connect Chamonix, France and Courmayeur, Italy, and become one of the major trans-Alpine transport routes between the two countries. In 1965, the tunnel opened to vehicle traffic with a length of.

1999 disaster.

In 1999, a transport truck caught fire in the tunnel beneath the mountain. In total 39 people were killed when the fire raged out of control. The tunnel was renovated in the aftermath to increase driver safety, reopening after three years.

Incidents involving children.

The record for the youngest person to climb Mont Blanc was set in 2009 by 10-year-old Asher Silver (UK).  In July 2014, an American entrepreneur and traveler Patrick Sweeney attempted to break the record with his nine-year-old son P.J. and 11-year-old daughter Shannon. They were caught in avalanche, luckily escaped death and decided not to pursue their attempt.  In August 2014, an unknown Austrian climber with his 5-year-old son were intercepted by mountain gendarmes at 3,200 metres and forced to turn around.  On 5 August 2017, 9-year-old Hungarian twins and their mother were rescued from 3,800 metres by helicopter while their father and family friend continued their summit attempt.

Elevation.

The summit of Mont Blanc is a thick, perennial ice-and-snow dome whose thickness varies. No exact and permanent summit elevation can therefore be determined, though accurate measurements have been made on specific dates. For a long time, its official elevation was. In 2002, the IGN and expert surveyors, with the aid of GPS technology, measured it to be.  After the 2003 heatwave in Europe, a team of scientists re-measured the height on 6 and 7 September. The team was made up of the glaciologist Luc Moreau, two surveyors from the GPS Company, three people from the IGN, seven expert surveyors, four mountain guides from Chamonix and Saint-Gervais and four students from various institutes in France. This team noted that the elevation was, and the peak was away from where it had been in 2002.  After these results were published, more than 500 points were measured to assess the effects of climate change and the fluctuations in the height of the mountain at different points. Since then, the elevation of the mountain has been measured every two years.  The summit was measured again in 2005, and the results were published on 16 December 2005. The height was found to be, more than the previous recorded height. The rock summit was found to be at, some west of the ice-covered summit.  In 2007, the summit was measured at and in 2009 at. In 2013, the summit was measured at and in 2015 at. From the summit of Mont Blanc on a clear day, the Jura, the Vosges, the Black Forest and the Massif Central mountain ranges can be seen, as well as the principal summits of the Alps.

Fatalities.

A 1994 estimate suggests there had been 6,000 to 8,000 alpinist fatalities in total, more than on any other mountain. Despite unsubstantiated claims recurring in media that "some estimates put the fatality rate at an average of 100 hikers a year", actual reported annual numbers at least since the 1990s are between 10 and 20: in 2017, fourteen people died out of 20,000 summit attempts and two remained missing; with 15 in 2018 as of August.  A French study on the especially risky "Goûter couloir, on the normal route on Mont Blanc" and necessary rescue operations found that between 1990 and 2011, there were 74 deaths "between the Tête Rousse refuge (3,187 m) and the Goûter refuge (3,830 m)". There were 17 more in 2012–15, none in 2016 and 11 in 2017.

Climbing routes.

Several classic climbing routes lead to the summit of Mont Blanc:

Refuges.

Impacts of climate change.

Recent temperature rises and heatwaves, such as those of the summers of 2015 and 2018, have had significant impacts on many climbing routes across the Alps, including those on Mont Blanc. For example, in 2015, the Grand Mulets route, previously popular in the 20th century, was blocked by virtually impenetrable crevasse fields, and the Gouter Hut was closed by municipal decree for some days because of very high rockfall danger, with some stranded climbers evacuated by helicopter.  In 2016 a crevasse opened at high altitude, also indicating previously unobserved glacial movements. The new crevasse forms an obstacle to be scaled by climbing parties on the final part of the itinerary to the top shared by the popular Goûter Route and the Grand Mulets Route.

Protection.

The Mont Blanc massif is being put forward as a potential World Heritage site because of its uniqueness and its cultural importance, considered the birthplace and symbol of modern mountaineering. It would require the three governments of Italy, France and Switzerland to make a request to UNESCO for it to be listed.  Mont Blanc is one of the most visited tourist destinations in the world, and for this reason, some view it as threatened. Pro-Mont Blanc (an international collective of associations for the protection of Mont Blanc) published in 2002 the book "Le versant noir du mont Blanc" (The black hillside of Mont Blanc), which exposes current and future problems in conserving the site.  In 2007, Europe's two highest toilets (at a height of 4,260 metres, 13,976 feet) were taken by helicopter to the top of Mont Blanc. They are also serviced by helicopter. They will serve 30,000 skiers and hikers annually, helping to alleviate the discharge of urine and faeces that spreads down the mountain face with the spring thaw, and turns it into 'Mont Marron'.  Global warming has begun to melt glaciers and cause avalanches on Mont Blanc, creating more dangerous climbing conditions.

Mont Blanc (; ; meaning "White Mountain") is the second-highest mountain in Europe after Mount Elbrus of Russia. It is the highest mountain in the Alps and Western Europe. It rises above sea level and is ranked 11th in the world in topographic prominence. The mountain stands in a range called the Graian Alps, between the regions of Aosta Valley, Italy, and Savoie and Haute-Savoie, France. The location of the summit is on the watershed line between the valleys of Ferret and Veny in Italy and the valleys of Montjoie, and Arve in France, on the border between the two countries.

Le mont Blanc (en ), dans le massif du Mont-Blanc, est le point culminant de la chaîne des Alpes. Avec une altitude de, il est le plus haut sommet d'Europe occidentale et le sixième sur le plan continental en prenant en compte les montagnes du Caucase, dont l'Elbrouz () est le plus haut sommet. Il se situe sur la frontière franco-italienne, entre le département de la Haute-Savoie (en France) et la Vallée d'Aoste (en Italie) ; cette frontière est l'objet d'un litige entre les deux pays.