The United States is the only state which divides the entire globe into military commands with a general or admiral in command of each region and designated forces. This practice began during World War II when global warfare forced the U.S. armed services to change from small, separate branches into an integrated armed force that deployed vast land, sea, and air forces around the globe. This practice of assigning U.S. military forces responsibility for specific regions worldwide is known as the Unified Command Plan (UCP).

The Goldwater-Nichols Department of Defense Reorganization Act of 1986 requires the Chairman of the Joint Chiefs of Staff to conduct a biennial review of the UCP to examine the force structure, missions, and responsibilities, including geographic boundaries of each unified command. The next review will take place in 2004.

From Oct. 1, 2002, The Unified Command Plan:

Creates a new combatant command, U.S. Northern Command, and assigns it the mission of defending the United States and supporting the full range of military assistance to civil authorities.

Shifts U.S. Joint Forces Command's geographic area of responsibility to the U.S. Northern Command and U.S. European Command. This enables U.S. Joint Forces Command to focus on transforming U.S. military forces and conducting joint force integration, training, experimentation, doctrine development and testing activities.

The Commander-in-Chief of Joint Forces Command will no longer serve as NATO's Supreme Allied Commander Atlantic.

The continental United States, Canada, Mexico, and portions of the Caribbean region (transferred from Southern Command) will be designated as U.S. Northern Command's area of responsibility. While Alaska will be included in this assignment, Alaskan Command forces will remain assigned to U.S. Pacific Command. The commander U.S. Northern Command will also be responsible for security cooperation and military coordination with Canada and Mexico.

Russia and the Caspian Sea will be included in the area of responsibility assigned to U.S. European Command, however U.S. Pacific Command will retain responsibilities for certain activities in Eastern Russia. Antarctica will be included in the area of responsibility assigned to U.S. Pacific Command.

This means that from Oct. 1, there will be ten Unified Commands (composed of units from two or more military services):

Geographical Responsibilities:

	Northern Command (USNORTHCOM)
	Pacific Command (USPACOM)
	Central Command (USCENTCOM)
	European Command (USEUCOM)
	Southern Command (USSOUTHCOM)

Functional Responsibilities:

	Special Operations Command (USSOCOM)
	Transportation Command (USTRANSCOM)
	Strategic Command (USSTRATCOM)
	Joint Forces Command (USJFCOM)

Source: Department of Defense