How the U.S. Army Works

By: Ed Grabianowski

Seal of the U.S. Army
Courtesy U.S. Army

The U.S. Army is a main branch of the U.S. military. With over one million Americans serving in the Army, Army National Guard and Army Reserves, and a 2007 budget of more than $110 billion, it's one of the largest military organizations in the world.

The Army's primary purpose is to protect the United States and its interests. This is accomplished by fighting in armed conflicts when the need arises, participating in peacekeeping and security duties and maintaining a state of readiness for war. While the Army does have units that utilize aircraft and watercraft, its main responsibility is land-based combat.

Two main branches make up the Army: the operational branch and the institutional branch. The operational branch conducts the more visible aspects of the Army's job, which involves combat and peacekeeping. The institutional branch of the Army is responsible for training and maintaining soldiers and equipment so the operational branch can do its job effectively.

Within the operational branch, there are two divisions:

  • The regular army, also known as the active Army. Its units may be deployed around the world at any given moment. Roughly 60 percent of the Army's troops are in the regular Army.

  • Reserve components, which comprises the U.S. Army Reserve and the Army National Guard. Soldiers (the official term for anyone in the Army) in the reserve typically train one weekend per month, with a two-week training period occurring once each year. These part-time soldiers may be called up to full-time whenever the Army needs them. Some are divided into units made wholly from reserves, while other reserve soldiers fill out the ranks of regular Army units.

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Today's Army is an all-volunteer force. While this generally results in high-quality soldiers (because they all actually want to be in the Army), it can be difficult to get enough recruits to keep the Army fully manned. In 2005, the Army fell short of recruiting goals, but met its recruiting benchmarks in 2006. The United States has used conscription (mandatory military service, also known as "the draft") several times in the past. Drafts were used in the War of 1812 and by both Union and Confederate forces during the American Civil War. The draft was instituted again during both World Wars, and was used during the Cold War in the late 1940s and early 1950s (the only time a peacetime draft was used). The last draft occured in 1973, during the war in Vietnam. Since 1980, the United States has used the Selective Service System to register all males when they reach age 18. This system is designed to make it easier for the government to find and enlist soldiers if a draft is reinstated. However, no one has been prosecuted for failing to register since the mid-1980s.

To supplement the active Army with reserves, Congress generally needs to have declared an emergency or a war, which gives the President the authority to call up those troops held in the reserves for the length of the situation plus six months. The President can also call up reserves without Congressional authority for a limited amount of time. In addition, the President can activate members of the National Guard. The length of time a National Guardsman can serve in active duty overseas has increased from six months to 24 months because of personnel shortages caused by the war in Iraq.

Next, we'll look at the Army's hierarchy.


Army Hierarchy

Like all military organizations, the U.S. Army follows a strict hierarchy. This establishes the chain of command through which virtually all Army orders and procedures flow. The President is the Commander-in-Chief of all U.S. armed forces. In wartime, he makes decisions based on recommendations from the Secretary of Defense and the Joint Chiefs of Staff, a committee of high-ranking officials from each branch of the armed forces.

The U.S. military is also divided into 10 Unified Combatant Commands (UCC). UCCs include forces from the Army as well as other military branches. Four of these commands are functional:

The remaining five commands are large geographic regions that encompass the entire globe. Each regional UCC is lead by a general and manned by a numbered field army. For example, the UCC responsible for North America, United States Northern Command, is manned by the Fifth Army. The rest of the regional commands:

This map of the world shows five of the six regional commands of the Unified Combat Commands.   United States Africa Command (USAFRICOM), created in February 2007 from parts of USEUCOM, USCENTCOM and USPACOM,  is scheduled to become operational in September 2008.
Photo courtesy U.S. Department of Defense

Within each field army are several corps; the corps themselves are made up of divisions. Formerly, the division was the "building block" of most Army deployments. When troops were needed somewhere in the world, the Army would send one or more divisions to do the job. However, a division is made up of more than 10,000 troops (including support personnel), and many situations faced by the modern army don't require that many soldiers.

As a result, the Army is undergoing a restructuring, scheduled to be completed in 2009, that will increase the flexibility of troop deployments. Once the restructuring is complete, the brigade will become the basic "Unit of Action" for the army. Made up of about 3,000 troops, each brigade will serve a specific purpose and will be completely autonomous, containing all the support and command personnel needed for the mission. Brigade types will include infantry, artillery, airborne and sustainment brigades, as well as Stryker brigades that will use the Army's versatile Stryker wheeled combat vehicles.

The 2nd Brigade Combat Team stands in formation at Camp Casey in Tongduchon, Korea.
Photo by Hu Son Yu/courtesy U.S. Army

Within each brigade, troops are further broken down into smaller groups:

  • Battalion - up to 1,000 soldiers
  • Company - approximately 100 soldiers
  • Platoon - up to 50 soldiers (this is the smallest unit lead by a commissioned officer)
  • Section or squad - Approximately eight soldiers
  • Fire Team - four soldiers

In peacetime, army leadership is more political than military. It is headed by the Secretary of the Army, a civilian position beneath the Secretary of Defense. The U.S. Army Chief of Staff advises the secretary. High-level army leadership is made up of commissioned officers, men and women who graduated from officer school and have been specially trained to be leaders. Warrant officers make up a middle class, in between commissioned officers and non-commissioned officers. Warrant officers often have more specialized roles than COs, and are afforded many of the same privileges of rank as COs. NCOs are enlisted soldiers who have moved up through the ranks by virtue of their experience, demonstrated abilities or simply time served in the army. Most units are lead in the field by sergeants.

Official Army Ranks and Abbreviations
Commissioned Officers
Warrant Officers
Enlisted Soldiers
General of the Army (GA)
Chief Warrant Officer 5 (CW5)
Sergeant Major of the Army (SMA)
General (GEN)
Chief Warrant Officer 4 (CW4)
Command Sergeant Major (CSM)
Lieutenant General (LTG)
Chief Warrant Officer 3 (CW3)
Sergeant Major (SM)
Major General (MG)
Chief Warrant Officer 2 (CW2)
First Sergeant (1SG)
Brigadier General (BG)
Warrant Officer 1 (WO1)
Master Sergeant (MSG)
Colonel (COL)
Sergeant First Class (SFC)
Lieutenant Colonel - (LTC)
Staff Sergeant (SSG)
Major (MAJ)
Sergeant (SGT)
Captain (CPT)
Corporal (CPL)
First Lieutenant (1LT)
Specialist (SPC)
Second Lieutenant (2LT)
Private First Class (PFC)
Private E-2 (PV2)
Private E-1 (PV1)

To learn more about the responsibilities of each Officer and Soldier ranking, check out U.S. Army Symbols and Insignia.

Learn about signing up for the Army and training in the next section.


Signing Up and Training

If you want to join the Army, you have a number of decisions to make. The first is whether to join the regular Army, the reserves or the National Guard. Within the regular Army, a potential soldier can opt to become an enlisted soldier, a warrant officer or a commissioned officer:


In general, the majority of potential recruits with criminal backgrounds, especially felonies, have not been allowed to join the Army. Exceptions, or waivers, have been granted on a case-by-case basis. But since 2003, the number of waivers given to recruits with criminal backgrounds has increased by about 65 percent in order to keep up with wartime demands [Source: New York Times]. This includes recruits who have been convicted of both serious misdemeanors (such as burglary and aggravated assault) and felonies (although those with multiple felonies, drug trafficking and other specific crimes are excluded).

The increase in waiver distribution has been controversial. According to Representative Martin T. Meehan, "By lowering standards, we are endangering the rest of our armed forces and sending the wrong message to potential recruits across the country" [Source: New York Times]. However, the military maintains that the waiver process is very selective, taking into account the nature of the crime, the age of the recruit when he committed it, his criminal records and recommendations from members of his community.

    ­Enlisted Soldier
    The bulk of all soldiers (roughly 84 percent) are enlisted, usually through a local recruiting office. United States citizens between the ages of 17 and 34 years old with a high school diploma (or the equivalent) and good physical health and fitness are eligible for enlistment. They must also receive such as a minimum 31 score on the Armed Services Vocational Aptitude Battery (ASVAB) test. To learn more about requirements, check out Web site or speak to a recruiter.

    Warrant Officer
    Warrant officers need to demonstrate a certain degree of technical skill, indicated by a minimum 110 score on the General Technical portion of the ASVAB. They must also be U.S. citizens between the ages of 18 and 33 with a high school diploma. The physical screening for warrant officers is more rigorous than for regular enlistment. Potential warrant officers must attend Warrant Officer Candidate School after completing basic training. Those who want to become helicopter pilots will attend Warrant Officer Flight Training instead.

    Commissioned Officer
    Commissioned officers are the top-ranking leaders in the Army. There are several paths to becoming a commissioned officer. You can join ROTC, or Reserve Officers' Training Corps. ROTC is a set of leadership courses than are taken in conjunction with regular college courses. Graduation from the ROTC program earns the soldier the rank of Second Lieutenant. Students can also attend West Point, an elite military academy with stringent entrance requirements and a very rigorous training and learning program. Graduating from West Point is a prestigious honor.

Photo courtesy U.S. Army
Cadets toss their caps into the air at the conclusion of their graduation ceremony at the United States Military Academy at West Point, New York.

    Potential soldiers with college degrees between the ages of 19 and 28 can attend Officer Candidate School, an intense 14-week training program at Fort Benning, Georgia. Officer Candidate School leads to service as an officer for a three-year minimum in the regular army, or six years in the reserves. Civilians with professional degrees may be eligible for a commissioned rank based on their levels of skill and experience.


All Army recruits except West Point cadets (who go through a longer, even more grueling training program) experience basic training, a nine-week program that hones a soldier's mental and physical abilities and teaches them how to function within the Army. Recruits learn to respect and obey higher ranking soldiers, built their endurance through obstacle courses and long runs in heavy gear, learn to maintain and fire military weapons and learn Army basics lik­e map reading and First Aid. Basic training is run by drill sergeants, specially-trained NCOs who motivate and teach recruits. No one would describe basic training as "fun," but most soldiers are proud to have gone through the experience. The fact that almost everyone in the Army has experienced basic training also serves to forge a bond between soldiers.

Photo courtesy U.S. Army
Drill Sergeant Primus Brown and recruits offer words of encouragement to a trainee negotiating the obstacle course at Fort Benning, Georgia.

­After basic training, soldiers move on to Advanced Individual Training (AIT). Here soldiers choose their career paths in the Army. Options include Infantry School, Engineer School, Field Artillery Center and Military Police School. A complete list of the AIT schools can be found here at the

We'll look at some basics of life in the Army next.


Army Life

A soldier's training is never completely finished. In the modern Army, mundane tasks formerly used as punishment or busy work for soldiers, such as preparing food for mess service or basic cleaning, are often performed by civilians under contract with the Army. This frees up soldiers' time, allowing them to take ongoing training courses. They may go through additional AIT schools to diversify their training or take leadership courses. Entire units can take special training courses together. The Army's goal is to keep soldiers focused on improving their skills and abilities so they can perform their jobs perfectly when peoples' lives are on the line.

The barracks at Fort Lewis, Washington.
Photo by Jason Kaye/courtesyU.S. Army
The U.S. Army barracks at Fort Lewis, Washington.

While a soldier's assignment ultimately depends on the needs of the Army, his area of expertise and his training, his family situation and specific requests may be taken into account. The Army has special programs for married couples who are both in the military and for other special situations, such as family hardships, that may require specific assignments. Other than these special cases, a soldier goes where the Army tells him to go.

The Army recently announced plans to replace its green, white and blue service uniforms with one blue service uniform, likely similar to the Army Blue uniform pictured here.
Photo courtesy U.S. Army
The Army recently announced plans to replace its green, white and blue service uniforms with one blue service uniform, likely similar to the Army Blue uniform pictured here. Other uniforms include the ACU (Army Combat Uniform) and the IPFU (Improved Physical Fitness Uniform).

All single enlisted soldiers live in barracks on an Army base when they first complete their training. Life in a barracks is similar to living in a college dorm: each soldier has at least one roommate and uses a communal bathroom and shower. Higher-ranked soldiers have the option of living off-base, using a military housing allowance. Married soldiers also have this option, although 24 percent of all military families live on base in Army-provided housing. The base itself includes enough provisions for daily life that soldiers and their families need never leave the base if they don't want to. Amenities include:

  • Post Exchange (PX) - The base store, where many consumer goods can be purchased
  • Gyms, pools and other exercise facilities
  • Movie theater
  • Restaurants, bars and clubs
  • Libraries
  • Golf courses, tennis courts and other recreational facilities

Army bases are scattered throughout the United States, and there are bases in South Korea, Japan, Belgium, Germany and Italy. Soldiers typically receive a new assignment every two or three years, so chances are they will eventually get to experience life outside the United States if they stay in the Army long enough.

As of 2006, the U.S. military is involved in a long-term war in Iraq. Although many soldiers train in non-combat specialties or request assignments to places other than Iraq or Afghanistan, there are never enough combat troops available. Therefore, every enlisted soldier has a chance of being sent to a combat zone. Once there, soldiers may be sent on combat missions as the need arises, regardless of their specialty. Make no mistake -- when you join the Army, there is a very real chance that you will see combat and the possibility of injury or death.

We'll look at life after a soldier leaves the Army in the next section.


Life After the Army

Medals and Decorations


The U.S. Army Medal of Honor
Photo courtesy U.S. Army











The U.S. Army traces its history to the American Revolutionary War. The formation of the Continental Army on June 14, 1775 is considered its official "birthday." The Continental Army was disbanded in 1784. However, conflicts between western settlers and Native Americans lead to the creation of the First American Regiment. After fighting several battles with Native Americans in the ensuing decades, the unit became the 1st Infantry. In 1815, several units, including the 1st Infantry, were combined to form the 3rd Infantry. So the modern 3rd Infantry is the only unit that can trace its lineage directly back to the formation of the U.S. Army.

Re-enactors from the Kansas Army National Guard represent four periods of conflict in the history of the U.S. Army during the 231st Army Birthday ceremony: the Revolutionary War, the Civil War, World War II and the Global War on Terrorism.
Re-enactors from the Kansas Army National Guard represent four periods of conflict in the history of the U.S. Army during the 231st Army Birthday ceremony in June 2006: the Revolutionary War, the Civil War, World War II and the Global War on Terrorism.

The Army was heavily involved in every U.S. military conflict in the 19th century. During the American Civil War, the U.S. Army became the Union Army. In the 20th century, U.S. Army soldiers took part in both World Wars, the Korean War, the Vietnam War and the first Persian Gulf War, as well as numerous smaller scale conflicts. Terrorist attacks and threats in the 21st century led the Army into Afghanistan and Iraq.

Because the National Guard is descended from various state militias that existed in the 1600s, it's technically older than the Army. Each National Guard unit is both a state and federal military unit. That is, the governor of each state commands the National Guard units stationed within that state, but the federal government can call on the units and bring them into action when needed. Federal authority supersedes state authority in such a situation. There are both part and full-time soldiers in the National Guard.

Since the end of the Vietnam War, the United States has held to a military doctrine called the Total Force Policy. This doctrine states that every branch of the military should be treated as a single force. Strategically, this means that the planning and deployment of the Air Force, Navy, Coast Guard and Marines should be intertwined with that of the Army. The policy is also designed to ensure the support of the American people when the nation goes to war, because the Army would be unable to effectively go to war without also activating the National Guard and Army Reserves. These two branches of the Army are considered more strongly associated with the average American citizen, especially the National Guard.

For lots more information about the U.S. Army and related topics, check out the links on the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links


  • The Army Historical Foundation. "First American Regiment."
  • "About the Army."
  • Stanton, Shelby L. "Soldiers: A Portrait of the United States Army." Howell Press (September 1991). 0943231221.