US Military 101 — Army, Navy, Air Force, Marines, and Coast Guard

Each Branch of the U.S. Military Has Its Own Unique Role

© The Balance 2018


The present U.S. military organizational structure is a result of the National Security Act of 1947. This is the same act that created the U.S. Air Force and restructured the War Department into the Department of Defense.

Each branch of the U.S. Armed Forces has its own unique role in defending the United States. Here's a rundown of each of them.

Department of Defense

The Department of Defense is headed by a civilian, the secretary of defense, who is appointed by the president of the United States and approved by the Senate. Under the Secretary of Defense, there are three military departments: the Department of the Army, the Department of the Air Force, and the Department of the Navy.

Each of these military departments is also headed up by a civilian service secretary, who are also appointed by the president.

There are five branches of the U.S. Armed Forces: the Army, Air Force, Navy, Marine Corps, and Coast Guard. The Marine Corps falls under the Department of the Navy, while the Coast Guard is not within the Department of Defense at all—it falls under the Department of Homeland Security, but is still considered part of the Armed Forces.

A four-star general known as the Army chief of staff commands the Army. The top military member in the Air Force is the Air Force chief of staff. The Navy is commanded by a four-star admiral called the chief of naval operations. A four-star officer takes on the role of commandant of the Coast Guard, as is the case with the commandant of the Marine Corps.

Joint Chiefs of Staff

These four flag officers (aside from the Coast Guard commandant, who is not part of the Department of Defense) also make up a group called the Joint Chiefs of Staff (JSC), which also includes the vice chairman and chairman of the joint chiefs of staff. The president nominates the chairman, who is approved by the Senate. For operational matters (such as war or conflict), the JCS bypasses the individual service secretaries and report directly to the secretary of defense and the president.

Army — Main US Ground Force

The Army is the main ground-force of the United States. Its primary function is to protect and defend the country and its interests with ground troops, armor (such as tanks), artillery, attack helicopters, tactical nuclear weapons, and other weapons.

The Army is the oldest U.S. military service, officially established by the Continental Congress on June 14, 1775. It’s also the largest of the military services. The Army is supported by two reserve forces which can be tapped for trained personnel and equipment during times of need: the Army Reserves, and the Army National Guard.

The primary difference between the two is that the Reserves are owned and managed by the federal government, and each state owns its own National Guard.

However, the president or the secretary of defense can activate state National Guard members into federal military service during times of need.

Air Force — Newest Branch

The Air Force is the youngest military service. Prior to 1947, the Air Force was a separate corps of the Army. The primary mission of the Army Air Corps was to support Army ground forces. However, World War II showed that air power had much more potential than simply supporting ground troops, so the Air Force was established as a separate service.

The primary mission of the Air Force is to defend the United States and its interests via air and space. It operates fighter aircraft, tanker aircraft, light and heavy bomber aircraft, transport aircraft, and helicopters. The Air Force is also responsible for all military satellites and controls strategic nuclear ballistic missiles. Like the Army, the active duty Air Force is supplemented by the Air Force Reserves and the Air National Guard.

Navy — Ruling the Seas

Like the Army, the Navy was officially established by the Continental Congress in 1775. The Navy's primary mission is to maintain and protect U.S. interests at sea.

In times of conflict, the Navy helps to supplement Air Force air power, since Navy aircraft carriers can often deploy to areas where fixed runways are impossible. An aircraft carrier usually carries about 80 aircraft, which are mostly made up of fighters or fighter-bombers.

Navy ships can attack land targets from miles away with very heavy guns and cruise missiles. Navy submarines allow stealth attacks on enemies from right off their shores.

The Navy is also primarily responsible for transporting Marines to areas of conflict. The Navy is supported in times of need by the Naval Reserves. However, unlike the Army and Air Force, there is no Naval National Guard (although a few states have established "naval militias").

Marine Corps — Amphibious Operations

Marines specialize in amphibious operations. Their primary specialty is to assault, capture, and control beachheads, which then provide a route to attack the enemy from almost any direction.

The Marines were officially established on Nov. 10, 1775, by the Continental Congress to act as a landing force for the Navy. In 1798, however, Congress established the Marine Corps as a separate service, although it still is managed under the Department of the Navy. While amphibious operations are their primary specialty, the Marines have expanded other ground-combat operations as well in recent years.

For combat operations, the Marine Corps likes to be self-sufficient, so it also has its own air power, consisting primarily of fighter aircraft and attack helicopters. But the Marines do use the Navy for logistical and administrative support; there are no doctors, nurses, or enlisted medics in the Marine Corps, for instance. Even medics that accompany the Marines into combat are specially trained Navy medics.

Coast Guard — Non-Military Branch

The U.S. Coast Guard is both the smallest branch of the Armed Forces and the only one that is technically not a part of the military, falling under the Department of Homeland Security rather than the Department of Defense. It was originally established as the Revenue Cutter Service in 1790. In 1915, it was reformed as the United States Coast Guard, under the Treasury Department. In 1967, the Coast Guard was transferred to the Department of Transportation. Legislation passed in 2002 transferred the Coast Guard to the Department of Homeland Security.

In peacetime, the Coast Guard is primarily concerned with law enforcement, boating safety, sea rescue, and illegal immigration control. However, the president can transfer part or all of the Coast Guard to the Department of the Navy in times of conflict.

The Coast Guard consists of ships, boats, aircraft, and shore stations that conduct a variety of missions. It is also supported by the Coast Guard Reserves, and a volunteer Coast Guard Auxiliary in times of need.

The Coast Guard is commanded by a four-star admiral known as the Coast Guard commandant.

Enlisted Personnel

Enlisted members perform the primary jobs that need to be done, trained to perform specific specialties in the military. As enlisted personnel progress up the nine ranks, they assume more responsibility and provide direct supervision to their subordinates.

Enlisted personnel in certain grades have special status. In the Army, Air Force, and Marine Corps, this status is known as Non-Commissioned Officer status, or NCO. In the Navy and Coast Guard, such enlisted are known as petty officers. In the Marine Corps, NCO status begins at the grade of E-4 (corporal).

In the Army and Air Force, enlisted personnel in the grades of E-5 through E-9 are NCOs. However, some Army E-4s are laterally promoted to corporal and are considered NCOs.

Also in the Army and Air Force, personnel in the grades of E-7 to E-9 are known as senior NCOs.

In the Marine Corps, those in the grades of E-6 through E-9 are known as staff NCOs.

In the Navy/Coast Guard, petty officers are those in the grades of E-4 through E-9. Those in the grades of E-7 to E-9 are known as chief petty officers.

Warrant Officers

Warrant Officers are highly trained specialists. This is where they differ from commissioned officers. Unlike commissioned officers, warrant officers remain in their primary specialty to provide specialized knowledge, instruction, and leadership to enlisted members and commissioned officers alike.

With few exceptions, one must be an enlisted member with several years of experience, recommended by their commander, and pass a selection board to become a warrant officer. The Air Force is the only service which does not have warrant officers — it eliminated the role when Congress created the grades of E-8 and E-9 in the late 1960s. The other services elected to retain the warrant ranks and shifted the emphasis from a promotion process for E-7s to a highly selective system for highly-skilled technicians.

Commissioned Officers

Commissioned officers are the top brass. Their primary function is to provide overall management and leadership in their area of responsibility. Unlike enlisted members and warrant officers, commissioned officers do not specialize as much (with certain exceptions such as pilots, doctors, nurses, and lawyers).

Commissioned officers must have a minimum of a four-year bachelor's degree. As they move up the ranks, if they want to get promoted, they will have to earn a master’s degree. Commissioned officers are commissioned through specific programs, such as through one of the military academies (West Point, Naval Academy, Air Force Academy, Coast Guard Academy), ROTC (Reserve Officer Training Corps), or OCS (Officer Candidate School)—called OTS (Officer Training School) in the Air Force.

There are also two basic types of commissioned officers: line and non-line. Non-line officers are non-combat specialists which include medical officers such as doctors and nurses, lawyers, and chaplains. Non-line officers cannot command combat troops as they are specialists and have different jobs and responsibilities.