U.S. Northern Command (USNORTHCOM)

A regional headquarters responsible for planning and conducting U.S. military activity in the continental United States, Alaska, Canada, Mexico, Puerto Rico, and the U.S. Virgin Islands.

United States Northern Command (NORTHCOM) was established in 2002 in response to the September 11, 2001, terrorist attacks in New York City and Washington, DC. Located at Peterson Air Force Base in Colorado Springs, Colorado, NORTHCOM is one of the nine combatant commands established and operated by the United States Department of Defense. Northern Command centralizes the homeland defense activities being conducted by other Defense Department agencies, by putting them under a single command. Organizationally, it is under the same command as North American Aerospace Defense Command.

According to the Department of Defense, Northern Command's mission is homeland defense and civil support. It conducts operations to deter, prevent, and defeat threats and aggression aimed at the United States, its territories, and interests within the assigned area of responsibility. It also provides military assistance to civil authorities, as directed by the president or secretary of defense. Like the other combatant commands, NORTHCOM does not maintain its own standing forces; rather, the troops are tasked to the command as needed. NORTHCOM's permanent staff consists of approximately 500 civilian and uniformed personnel.

Northern Command's operations on domestic soil are regulated by the Posse Comitatus Act. The act limits the role of the military in domestic affairs, including the prohibition of the military from participating in the interdiction of vehicles, vessels, and aircraft; execution of surveillance, searches, pursuits, and seizures; or arresting individuals in lieu of civilian law-enforcement agencies. A congressional exception can allow the military to assist civilian law-enforcement agencies at the federal, state, and local levels on a case-specific basis.