war i was at the second battle of ypres, on april 22, 1915, when the germans attacked french, canadian and algerian troops with chlorine gas released from canisters and carried by the wind towards the allied trenches. a total 50,965 tons of pulmonary, lachrymatory, and vesicant agents were deployed by both sides of the conflict, including chlorine, phosgene, and mustard gas. official figures declare about 1.3 million casualties directly caused by chemical warfare agents during the course of the war. of these, an estimated 100,000–260,000 casualties were civilians. nearby civilian towns were at risk from winds blowing the poison gases through. civilians rarely had a warning system put into place to alert their neighbors of the danger. in addition to poor warning systems, civilians often did not have access to effective gas masks. football team of british soldiers with gas masks, western front, 1916 world war i-era chemical ammunition is still found, unexploded, at former battle, storage, or test sites and poses an ongoing threat to inhabitants of belgium, france and other countries. camp american university where american chemical weapons were developed and later buried, has undergone 20 years of remediation efforts. after the war, the most common method of disposal of chemical weapons was to dump them into the nearest large body of water. as many as 65,000 tons of chemical warfare agents may have been dumped in the baltic sea alone; agents dumped in that sea included mustard gas, phosgene, lewisite (β-chlorovinyldichloroarsine), adamsite (diphenylaminechloroarsine), clark i (diphenylchloroarsine) and clark ii (diphenylcyanoarsine). over time the containers corrode, and the chemicals leaked out. on the sea floor, at low temperatures, mustard gas tends to form lumps within a "skin" of chemical byproducts. these lumps can wash onto shore, where they look like chunks of waxy yellowish clay. they are extremely toxic, but the effects may not be immediately apparent. interwar years between world war i and world war ii, chemical agents were occasionally used to subdue populations and suppress rebellion. in 1925, 16 of the world's major nations signed the geneva protocol, thereby pledging never to use gas in warfare again. notably, while the united states delegation under presidential authority signed the protocol, it was not ratified until the 1970’s alleged british use in mesopotamia it has been alleged that the british used chemical weapons in mesopotamia during the iraqi revolt of 1920. noam chomsky claimed that winston churchill at the time was keen on chemical weapons, suggesting they be used "against recalcitrant arabs as an experiment", and that he stated to be "strongly in favour of using poisoned gas against uncivilised tribes". according to some historians, including geoff simons and charles townshend, the british used chemical weapons in the conflict, while according to lawrence james and niall ferguson the weapons were agreed by churchill but eventually not used; r.m. douglas of colgate university also observed that churchill's statement had served to convince observers of the existence of weapons of mass destruction which were not actually there. soviet use in tambov, central-asia, and china lenin's soviet government employed poison gas in 1921 during the tambov rebellion. an order signed by military commanders tukhachevsky and vladimir antonov-ovseyenko stipulated, "the forests where the bandits are hiding are to be cleared by the use of poison gas. this must be carefully calculated, so that the layer of gas penetrates the forests and kills everyone hiding there." in 1930s soviets used mustard gas deployed from planes against basmachi rebels in central-asia. during the soviet invasion of xinjiang in 1934, ma zhongying's 36th division put up a fierce resistance at the battle of dawan cheng, but was forced to retreat after soviets delivered mustard gas from planes. chinese use a ‘chemical arms race' developed during the warlord era. the first chemical weapons were imported by a minor hunan warlord, who bought two small cases of‘gas-producing shells’ in august 1921. marshal ts’aok’un, approached a british-owned chemical company in tientsin in 1923; he attempted to order gas bombs, but as far as is known they turned down his proposal. in 1925, chang tso-lin had a chemical plant built in mukden and hired german and russian experts to produce chlorine, phosgene and mustard gas, in the same year feng yu-hsiang also set up a ‘special arsenal’ to produce chemical weapons designed by soviet and german experts. all of these efforts appear to have failed. there was one reported incident of chemical warfare when chang tso-lin’s aircraft dropped gas bombs’ on the forces of wu pei-fu; who branded the use of these bombs as inhumane. spanish use in morocco combined spanish and french forces dropped mustard gas bombs against berber rebels and civilians during the rif war in spanish morocco (1921–1927). these attacks marked the first widespread employment of gas warfare in the post-wwi era. the spanish army indiscriminately used phosgene, diphosgene, chloropicrin and mustard gas against civilian populations, markets and rivers. spain signed the geneva protocol in 1925, which prohibited the use of chemical and biological weapons in international conflicts, while simultaneously employing these weapons across the mediterranean. in a telegram sent by the high commissioner of spanish morocco dámaso berenguer on august 12, 1921 to the spanish minister of war, berenguer stated: "i have been obstinately resistant to the use of suffocating gases against these indigenous peoples but after what they have done, and of their treacherous and deceptive conduct, i have to use them with true joy." according to military aviation general hidalgo de cisneros in his autobiographical book cambio de rumbo, he was the first warfighter to drop a 100-kilogram mustard gas bomb from his farman f60 goliath aircraft in the summer of 1924. about 127 fighters and bombers flew in the campaign, dropping around 1,680 bombs each day. the mustard gas bombs were brought from the stockpiles of germany and delivered to melilla before being carried on farman f60 goliath airplanes. historian juan pando has been the only spanish historian to have confirmed the usage of mustard gas starting in 1923. spanish newspaper la correspondencia de españa published an article called cartas de un soldado (letters of a soldier) on august 16, 1923 which backed the usage of mustard gas. some have cited the chemical weapons used in the region as the main reason for the widespread occurrence of cancer among the population. in 2007, the catalan party of the republican left (esquerra republicana de catalunya) passed a bill to the spanish congress of deputies requesting spain to acknowledge the "systematic" use of chemical weapons against the population of the rif mountains; however, the bill was rejected by 33 votes from the governing socialist labor party and the opposition right-wing popular party. italian use in libya and ethiopia in violation of the geneva protocol, italy used mustard gas and other "gruesome measures" against senussi forces in libya (see pacification of libya, italian colonization of libya). poison gas was used against the libyans as early as january 1928 the italians dropped mustard gas from the air. beginning in october 1935 and continuing into the following months fascist italy used mustard gas against the ethiopians during the second italo-abyssinian war in violation of the geneva protocol. italian general rodolfo graziani first ordered the use of chemical weapons at gorrahei against the forces of ras nasibu. benito mussolini personally authorized graziani to use chemical weapons. chemical weapons dropped by warplane "proved to be very effective" and was used "on a massive scale against civilians and troops, as well as to contaminate fields and water supplies." among the most intense chemical bombardment by the italian air force in ethiopia occurred in february and march 1936, although "gas warfare continued, with varying intensity, until march 1939." j. f. c. fuller, who was present in ethiopia during the conflict, stated that mustard gas "was the decisive tactical factor in the war." some estimate that up to one-third of ethiopian casualties of the war were caused by chemical weapons. the italians' deployment of mustard gas prompted international criticism. in april 1936, british prime minister stanley baldwin told parliament: "if a great european nation, in spite of having given its signature to the geneva protocol against the use of such gases, employs them in africa, what guarantee have we that they may not be used in europe?" mussolini initially denied the use of chemical weapons; later, mussolini and italian government sought to justify their use as lawful retaliation for ethiopian atrocities. after the liberation of ethiopia in 1941, ethiopia repeatedly but unsuccessfully sought to prosecute italian war criminals. the allied powers excluded ethiopia from the united nations war crimes commission (established 1942) because the british feared that ethiopia would seek to prosecute pietro badoglio, who had ordered the use of chemical gas in the second italo-abyssinian war, but later "became a valuable ally against the axis powers" after the fascist regime of mussolini fell and, after the rise of the italian social republic, italy became a co-belligerent of the allies. in 1946, the ethiopians under haile selassie again sought "to prosecute senior italian officials who had sanctioned the use of chemical weapons and had committed other war crimes such as torturing and executing ethiopian prisoners and citizens during the italian-ethiopian war." these attempts failed, in large part because britain and the u.s. wished to avoid alienating the italian government at a time when italy was seen as key to containing the soviet union. following world war ii, the italian government denied that italy had ever used chemical weapons in africa; only in 1995 did italy formally acknowledge that it had used chemical weapons in colonial wars. nerve agents the chemical structure of sarin nerve gas, developed in germany in 1939 shortly after the end of world war i, germany's general staff enthusiastically pursued a recapture of their preeminent position in chemical warfare. in 1923, hans von seeckt pointed the way, by suggesting that german poison gas research move in the direction of delivery by aircraft in support of mobile warfare. also in 1923, at the behest of the german army, poison gas expert dr. hugo stoltzenberg negotiated with the ussr to build a huge chemical weapons plant at trotsk, on the volga river. collaboration between germany and the ussr in poison gas continued on and off through the 1920s. in 1924, german officers debated the use of poison gas versus non-lethal chemical weapons against civilians. chemical warfare was revolutionized by nazi germany's discovery of the nerve agents tabun (in 1937) and sarin (in 1939) by gerhard schrader, a chemist of ig farben. ig farben was germany's premier poison gas manufacturer during world war ii, so the weaponization of these agents cannot be considered accidental. both were turned over to the german army weapons office prior to the outbreak of the war. the nerve agent soman was later discovered by nobel prize laureate richard kuhn and his collaborator konrad henkel at the kaiser wilhelm institute for medical research in heidelberg in the spring of 1944. the germans developed and manufactured large quantities of several agents, but chemical warfare was not extensively used by either side. chemical troops were set up (in germany since 1934) and delivery technology was actively developed. world war ii imperial japanese army japanese special naval landing force wearing gas masks and rubber gloves during a chemical attack near chapei in the battle of shanghai despite the 1899 hague declaration iv, 2 – declaration on the use of projectiles the object of which is the diffusion of asphyxiating or deleterious gases, article 23 (a) of the 1907 hague convention iv – the laws and customs of war on land, and a resolution adopted against japan by the league of nations on may 14, 1938, the imperial japanese army frequently used chemical weapons. because of fear of retaliation, however, those weapons were never used against westerners, but against other asians judged "inferior" by imperial propaganda. according to historians yoshiaki yoshimi and kentaro awaya, gas weapons, such as tear gas, were used only sporadically in 1937 but in early 1938, the imperial japanese army began full-scale use of sneeze and nausea gas (red), and from mid-1939, used mustard gas (yellow) against both kuomintang and communist chinese troops. according to historians yoshiaki yoshimi and seiya matsuno, the chemical weapons were authorized by specific orders given by emperor hirohito himself, transmitted by