The United States Armed Forces are the military forces of the United States of America. It consists of the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is the commander-in-chief of the Armed Forces and forms military policy with the Department of Defense (DoD) and Department of Homeland Security (DHS), both federal executive departments, acting as the principal organs by which military policy is carried out. All six armed services are among the eight uniformed services of the United States.
From its inception during the American Revolutionary War, the U.S. Armed Forces have played a decisive role in the history of the United States. It helped forge a sense of national unity and identity through its victories in the First Barbary War and the Second Barbary War. It played a critical role in the American Civil War, keeping the Confederacy from seceding from the republic. The National Security Act of 1947, adopted following World War II, created the modern U.S. military framework. The Act established the National Military Establishment, headed by the secretary of defense; and created the United States Air Force and the National Security Council. It was amended in 1949, renaming the National Military Establishment the Department of Defense, and merged the cabinet-level Department of the Army, Department of the Navy, and Department of the Air Force, into the Department of Defense.
The U.S. Armed Forces are one of the largest military forces in terms of personnel. It draws its personnel from a large pool of paid volunteers. Although conscription has been used in the past, it has not been used since 1973. The Selective Service System retains the power to conscript males, and requires that all male citizens and residents residing in the U.S. between the ages of 18–25 register with the service.
The U.S. Armed Forces are considered the world's most powerful military. The military budget of the United States was US$693 billion in 2019, the highest in the world. In 2018, that accounted for 36 percent of the world's defense expenditures. 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 enables a widespread deployment of the force around the world, including around 800 military bases outside the United States. The U.S. Air Force is the world's largest air force, the U.S. Navy is the world's largest navy by tonnage, and the U.S. Navy and the U.S. Marine Corps combined are the world's second largest air arm. In terms of size, the U.S. Coast Guard is the world's 12th largest maritime force. The U.S. as of FY2019 has about 14,061 aircraft in its military inventory.