United States Armed Forces

The United States Armed Forces are the military forces of the United States. United States federal law establishes six armed forces: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard, each assigned specific roles and operational domains. With the exception of the Coast Guard, which operates under the Department of Homeland Security (DHS) in peacetime, the services are organized under the Department of Defense (DoD).

Established during the American Revolutionary War, the Army and the Navy, and later the other services, have played a decisive role in the country's history. They contributed to early national consolidation through conflicts such as the Barbary Wars and the War of 1812, shaped the country's territorial evolution, and were involved in major conflicts including the American Civil War, World War I, World War II, the Cold War, and the war on terror. The National Security Act of 1947 reorganized the military establishment by creating the DoD, the Air Force, and the National Security Council; in 1949, an amendment to the act merged the cabinet-level departments of the Army, Navy, and Air Force into the DoD. formalizing a unified defense structure under civilian control. The Space Force was established in 2019 as the newest branch.

The president of the U.S. serves as commander-in-chief and exercises authority over the armed forces through the DoD and, for the Coast Guard in peacetime, the DHS. Since 1973, the United States has maintained an all-volunteer force, although the Selective Service System remains authorized to conscript most male citizens and residents aged 18 and 25 to register. All six services are also among the eight uniformed services of the United States. The armed forces consist of active-duty personnel, Reserve components, and the National Guard.

The U.S. Armed Forces are widely considered the world's most powerful and most advanced military. The military expenditure of the U.S. was US$997 billion in 2024, the highest in the world, accounting for 37% of the world's defense expenditures. The personnel size of the six armed forces together ranks them among the world's largest state armed forces. The U.S. Armed Forces has significant capabilities in both defense and power projection due to its large budget, resulting in advanced and powerful technologies which enable widespread deployment of the force globally, including around 800 military bases around the world.