FAQ: What Are the US Military Branches?

Updated November 23, 2022

If you are considering service in the military, there is a lot you should know before you visit a recruiter. Understanding the purpose of the United States armed forces and each of its different branches can help you choose the service branch that is right for your career.

In this article, we discuss what the military is and the different service branches that make up the U.S. armed forces.

What is the military?

The U.S. military includes six branches that are sworn to defend the safety, security and best interests of the country. The military’s primary responsibility is to protect and defend the U.S. during a time of war, but the military also performs other missions. Members of the military may be called upon to serve internationally, known as a deployment, in more than 100 countries including Germany, the United Kingdom, Italy, Brazil, South Korea, Japan, Australia, Iraq and Afghanistan.

Not every deployment serves the purpose of defending the U.S. in combat. Members of the military may be involved in rescue operations, natural disaster relief, medical assistance in impoverished areas, food and humanitarian relief, security at international U.S. embassies, policing in volatile areas, training allied militaries, law enforcement and piracy and drug interdiction.

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What are the different types of military service?

Military service members are generally categorized as active duty, reserve or guard forces, veterans or retirees. Active duty members are full-time members of the military. Junior members on active duty usually live in their units' barracks, base housing, homes near their duty station or on ships.

Reserve and guard force members are part-time members who usually work civilian jobs but can be activated for full-time military service during a time of crisis. Reserve service members usually train one weekend per month and two weeks per year.

Veterans and retirees are former service members who are no longer enlisted in the military.

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Who is in command of the military?

The Department of Defense (DoD) is in control of the Army, Marine Corps, Navy, Air Force, and Space Force, while the Department of Homeland Security is in command of the Coast Guard during peacetime. The Secretary of the Department of Defense is in charge of all the branches except for the Coast Guard, with final command falling to the President of the United States, who is also known as the Commander-in-Chief.

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Military branches

There are six main service branches of the military and each branch has a role in maintaining the U.S. national defense posture. The six main branches of the military are:

Air Force

This branch includes the Air Force, Air Force Reserve and Air National Guard. The Air Force was part of the Army until it was made into its own branch in 1947. Its primary purpose is to defend the United States through air and space. To accomplish this, the Air Force uses planes, helicopters and satellites to maintain air superiority. The Air Force also controls an arsenal of strategic nuclear ballistic missiles.

The Air Force Reserve and Air National Guard are reserve members who can be called upon by the Air Force for full-time service when needed.


This branch includes the Army, Army Reserve and Army National Guard. The Army, the oldest U.S. military service branch, was established June 14, 1775, by the Continental Congress during the Revolutionary War. The Army is also the largest U.S. military branch. The primary purpose of the Army is to protect and defend the United States and its interests on land. To accomplish this, the Army can deploy light infantry, tanks, artillery, helicopters and to move into an area, clear it and hold a position.

Like the Air Force, the Army Reserve and Army National Guard are reserve members who can be activated by the Army for full-time service when needed. The difference between the Army Reserve and Army National Guard is that the Reserves are controlled by the federal government and the National Guard is controlled by the individual states. Even though the National Guard is controlled by the states, its members can still be called upon for national service by the Secretary of Defense in a time of need.

Coast Guard

This branch is made up of the Coast Guard and Coast Guard Reserve. The Coast Guard is the smallest of the military branches but can become part of the Navy during times of war. The primary mission of the Coast Guard is to protect domestic waterways. During peace times, Coast Guard members may be involved in missions that include law enforcement, drug interdiction, boating safety, water rescues and illegal immigration deterrence.

Marine Corps

This branch is made up of the Marine Corps and the Marine Corps Reserve. Like the Army, the Marine Corps was established by the Continental Congress on Nov. 10, 1775. The Marine Corps is known as the U.S.’s rapid-reaction force and are often some of the first members to enter combat. Members of the Marine Corps are trained to fight both on land and at sea. They are relied upon to make amphibious landings, attacking and capturing beachheads to make an attack pathway to the enemy from nearly any direction.


This branch is made up of the Navy and the Navy Reserve. Like the Army, the Navy was also established by the Continental Congress in 1775. The primary purpose of the Navy is to protect U.S. interests on the oceans and seas around the world and make them safe for both travel and trade. To accomplish this, the Navy deploys a diverse fleet of aircraft carriers, battleships, submarines and aircraft.

During times of war, the Navy can be used to supplement the Air Force because they can use aircraft carriers to deploy the Air Force to areas where fixed runways can’t be established. The Navy is also used to transport Marines to areas of conflict. Navy Reserve members can be called upon by the Navy for full-time service during times of need.

Space Force

The Space Force was established on Dec. 20, 2019, as a Department of the Air Force and is the smallest branch of the services. There are only active-duty troops in the Space Force with no Reserve or Guard component yet established. The Space Command oversees critical satellite infrastructure, missile warning systems, intelligence gathering capabilities and meteorology.

The Space Force is a military service that organizes, trains and equips forces to protect U.S. and allied interests in space and to provide space capabilities to the joint force. Branch responsibilities include acquiring military space systems, maturing the military doctrine for space power and organizing space forces to present to the U.S. Defense Department’s Combatant Commands.

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