The United States Armed Forces are the military forces of the United States of America. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard. The U.S. has a strong tradition of civilian control of the military. 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. The DoD is headed by the Secretary of Defense, who is a civilian and Cabinet member. The Defense Secretary is second in the military's chain of command, just below the President, and serves as the principal assistant to the President in all DoD-related matters. To coordinate military action with diplomacy, the President has an advisory National Security Council headed by a National Security Advisor. Both the President and Secretary of Defense are advised by a seven-member Joint Chiefs of Staff, which includes the head of each of the Defense Department's service branches as well as the chief of the National Guard Bureau. Leadership is provided by the Chairman of the Joint Chiefs of Staff and the Vice Chairman of the Joint Chiefs of Staff. The Commandant of the Coast Guard is not a member of the Joint Chiefs of Staff.
All of the branches work together during operations and joint missions, under the Unified Combatant Commands, under the authority of the Secretary of Defense with the exception of the Coast Guard. The Coast Guard falls under the administration of the Department of Homeland Security and receives its operational orders from the Secretary of Homeland Security. The Coast Guard may be transferred to the Department of the Navy by the President or Congress during a time of war. All five armed services are among the seven uniformed services of the United States; the others are the U.S. Public Health Service Commissioned Corps and the National Oceanic and Atmospheric Administration Commissioned Corps.
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 and 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 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 and National Security Council.
The U.S. military is one of the largest militaries in terms of number of personnel. It draws its manpower 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 2013, the U.S. spends about $554.2 billion annually to fund its military forces, and appropriates approximately $88.5 billion to fund Overseas Contingency Operations. Put together, the U.S. constitutes roughly 39 percent of the world's military expenditures. The U.S. Armed Forces as a whole possess large quantities of advanced and powerful equipment, along with widespread placement of forces around the world, giving them significant capabilities in both defense and power projection.