US Military soldiers conduct live fire machine gun exercise. The United States Armed Forces are the federal armed forces of the United States. They consist of the Army, Marine Corps, Navy, Air Force, and Coast Guard. The President of the United States is the military's overall head, and helps form military policy with the U.S. Department of Defense (DoD), a federal executive department, acting as the principal organ by which military policy is carried out.
From the time of its inception, the military played a decisive role in the history of the United States. A sense of national unity and identity was forged as a result of victory in the First Barbary War and the Second Barbary War. Even so, the Founders were suspicious of a permanent military force. It played an important role in the American Civil War, where leading generals on both sides were picked from members of the United States military. Not until the outbreak of World War II did a large standing army become officially established. The National Security Act of 1947, adopted following World War II and during the Cold War's onset, created the modern U.S. military framework; the Act merged the previously Cabinet-level Department of War and the Department of the Navy into the National Military Establishment (renamed the Department of Defense in 1949), headed by the Secretary of Defense; and created the Department of the Air Force (within the Defense Department) and the National Security Council.
The U.S. military is one of the largest militaries in terms of number of personnel. It draws its personnel from a large pool of paid volunteers; although conscription has been used in the past in various times of both war and peace, it has not been used since 1972. As of 2016, the United States spends about $580.3 billion annually to fund its military forces and Overseas Contingency Operations. Put together, the United States constitutes roughly 40 percent of the world's military expenditures. For the period 2010–14, the Stockholm International Peace Research Institute (SIPRI) found that the United States was the world's largest exporter of major arms, accounting for 31 percent of global shares. The United States was also the world's eighth largest importer of major weapons for the same period. The U.S. military has significant capabilities in both defense and power projection due to its large budget, resulting in advanced and powerful equipment, and its widespread deployment of force around the world, including about 800 military bases in foreign locations. Added to this, the largest air force in the world is the U.S. Air Force. Moreover, the world’s second largest air force is the U.S. Navy and the Marine Corps combined.