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. All five armed services are among the seven uniformed services of the United States.
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, continuing to serve as the Armed Forces of the federal government, although a number of its officers resigned to join the Confederate Army and Navy. 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.
Main article: Military history of the United States
The history of the U.S. military dates to 1775, even before the Declaration of Independence marked the establishment of the United States. The Continental Army, Continental Navy, and Continental Marines were created in close succession by the Second Continental Congress in order to defend the new nation against the British Empire in the American Revolutionary War.
These forces demobilized in 1784 after the Treaty of Paris ended the War for Independence. The Congress of the Confederation created the United States Army on 3 June 1784, and the United States Congress created the United States Navy on 27 March 1794, and the United States Marine Corps on 11 July 1798. All three services trace their origins to the founding of the Continental Army (on 14 June 1775), the Continental Navy (on 13 October 1775) and the Continental Marines (on 10 November 1775), respectively. The 1787 adoption of the Constitution gave the Congress the power to "raise and support armies", "provide and maintain a navy", and to "make rules for the government and regulation of the land and naval forces", as well as the power to declare war. The United States President is the U.S. military's commander-in-chief.
Rising tensions at various times with Britain and France and the ensuing Quasi-War and War of 1812 quickened the development of the U.S. Navy (established 13 October 1775) and the United States Marine Corps (established 10 November 1775). The U.S. Coast Guard dates its origin to the founding of the Revenue Cutter Service on 4 August 1790; that service merged with the United States Life-Saving Service in 1915 to establish the Coast Guard. The United States Air Force was established as an independent service on 18 September 1947; it traces its origin to the formation of the Aeronautical Division, U.S. Signal Corps in 1907 and was part of the Army before becoming an independent service.