United States Northern Command (USNORTHCOM) is a Unified Combatant Command of the U.S. military tasked with providing military support for civil authorities in the U.S., and protecting the territory and national interests of the United States within the contiguous United States, Alaska, (not Hawaii), Puerto Rico, Canada, Mexico (and the air, land and sea approaches to these areas). It is the U.S. military command which, if applicable, would be the primary defender against a mainland invasion of the United States.