United States Pacific Command (USPACOM) is a unified combatant command of the United States armed forces responsible for the Indo-Asia-Pacific region. It is the oldest and largest of the unified combatant commands. Its commander, the senior U.S. military officer in the Pacific, is responsible for military operations in an area which encompasses more than 100 million square miles, or roughly 50 percent of the Earth’s surface, stretching from the waters off the west coast of the United States to the western coastal boarder of India, from the Arctic to the Antarctic. The Commander reports to the President of the United States through the Secretary of Defense and is supported by Service component and subordinate unified commands, including U.S. Army Pacific, U.S. Pacific Fleet, U.S. Pacific Air Forces, U.S. Marine Forces Pacific, U.S. Forces Japan, U.S. Forces Korea, Special Operations Command Korea, and Special Operations Command Pacific. The USPACOM headquarters building, the Nimitz-MacArthur Pacific Command Center, is located on Camp H.M. Smith, Hawai’i.