
All branches are part of the United States Uniformed Services and are under civilian control with the President serving as Commander-in-chief. All branches except the Coast Guard are part of the Department of Defense, which is under the authority of the Secretary of Defense, who is also a civilian. The Coast Guard falls under the authority of the Department of Homeland Security. During wartime, the Coast Guard may be placed under the Department of Defense through the Department of the Navy. There are also other military forces in the United States which fall solely under the individual control of each state, the State Defense Forces, which are not part of the Department of Defense. The United States Marine Corps is the only offical branch that is part of another military branch, as it was created as and still is a part of the Department of the Navy.
As of May 2007, about 1,426,705 people are on active duty in the military with an additional 1,458,400 people in the seven reserve components. As it is currently a volunteer military, there is no conscription. Women are not allowed to serve in some combatant positions, but they do serve in combat areas where they can and do come under enemy fire.
Under the United States Constitution, the President of the United States is the Commander-in-Chief of the Armed Forces. To coordinate military action with diplomacy, the President has an advisory National Security Council headed by a National Security Advisor. Under the President is the United States Secretary of Defense, a Cabinet Secretary responsible for the Department of Defense. Both the President and Secretary of Defense are advised by the Joint Chiefs of Staff, which includes the service branch chiefs led by the Chairman of the Joint Chiefs of Staff and the Vice Chairman of the Joint Chiefs of Staff.
Much of U.S. military capability is involved in logistics and transportation, which enable rapid buildup of forces as needed. The Air Force maintains a large fleet of C-5 Galaxy, C-17 Globemaster, and C-130 Hercules transportation aircraft with a substantial fleet of aerial refueling tankers. The Marine Corps maintains Marine Expeditionary Units at sea with the Navy's Atlantic and Pacific Fleets. The Navy's 11 active aircraft carriers, combined with a military doctrine of power projection, enables a flexible response to potential threats.
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