The Army, Navy, and Marine Corps were established in 1775, in concurrence with the American Revolution. The War Department was established in 1789, and was the precursor to what is now the Department of Defense.

The Department of the Navy, and the U.S. Coast Guard, were founded in 1798.

Congress, in 1947, established a civilian, Cabinet-level Secretary of Defense to oversee an also newly created National Military Establishment.

The U.S. Air Force was also created, along with a new Department of the Air Force. The War Department was converted to the Department of the Army.

Finally, the three services, Army, Navy, and Air Force, were placed under the direct control of the new Secretary of Defense.

In 1949, an amendment to the Act consolidated further the national defense structure, creating what is now known as the Department of Defense, and withdrawing cabinet-level status for the three Service secretaries.

Mission The President of the United States, along with the Secretary of Defense and the National Security Council, determines the security needs of the nation and then take courses of action to ensure that they are met. The President, in the constitutional role as commander-in-chief of the armed forces, is the senior military authority in the nation and as such is ultimately responsible for the protection of the United States from all enemies, foreign and domestic.

As part of the Constitution’s system of checks and balances, the budget of the DoD must be approved by the U.S. Congress. This is accomplished by working with various committees of both houses, primarily those dealing with funding, military operations, and intelligence. Their decisions affect the function of the armed forces and range from setting civilian pay raises to funding major troop deployments.