Maintains military forces to deter war and to protect the security of the country. Website provides information about the Air Force, Army, Marine Corps, Navy, and Space Force. Note that the Coast Guard is part of the Navy during conflicts and part of Homeland Security in times of peace; the National Guard is a state-based reserve force which can be activated for federal missions. Also provides answers to frequently asked questions and links to additional resources.

United States Department of Defense | United States Department of Defense

The U.S. Air Force defends the United States through control and exploitation of air and space. Airmen fly and maintain aircraft, such as  long-range bombers, supersonic fighters, Airborne Warning and Control System (AWACS) aircraft and many others to protect the interests of America and American allies. The Air Force is organized throughout the world and provides combat aircraft, airlift, refueling, reconnaissance and other support to the Unified Combatant Commands. 

Air Force

The U.S. Army's mission is to protect the security of the United States and it's resources through land-based operations throughout the world. The army also provides the infrastructure necessary to raise, train, equip, deploy and ensure the readiness of all of its forces; and soldiers work in a variety of institutional jobs ranging from general administration to the operations and maintenance of the Army's many thousands of weapons, vehicles, aircraft carriers and technical electronic systems. 

Army

The U.S. Marine Corps is trained, organized and equipped for offensive amphibious employment as a "force in readiness". Its primary specialty is to assault, capture and control beach heads, which then provide a route to attack the enemy from almost any direction. The Marine Corps also conducts operations on land and in the air in connection with naval campaigns; and is responsible for providing detachments for service aboard certain types of naval vessels, as well as security forces for naval shore installations and U.S. diplomatic missions in foreign countries. The Marines are often the first to fight entering combat zones very early in a battle, often prior to other services.

Marine Corps

The National Guard is a unique state-based military force shared by the state and federal government. Members of the Army and Air National Guard perform duty a minimum of 39 days per year but often much more. They can be called upon to augment active military forces in times of national emergency and serve their states and local communities when natural disasters and other contingencies occur. When on state duty (or state and federal shared duty), they are under the tactical and administrative control of the governor. When mobilized or performing strictly federal duty, they are under the control of the President as Commander-in-Chief. 

National Guard

The U.S. Navy trains and equips combat-ready Naval forces who are charged with conducting military operations at sea. The Navy defends the right to travel and trade freely on the world's oceans and protects the country and national interests overseas during times of international conflict. Sailors serve on ships at sea, on submarines, in aviation positions on land and sea and on shore bases around the world.

Navy

The principal executive divisions of the federal government of the United States, headed by a secretary who is a member of the President's cabinet, the agencies within them and the independent establishments and corporations that fall outside the cabinet structure.