The first woman to lead one of the largest U.S. military commands officially began the job on Friday. Air Force General Lori Robinson is the new head of the U.S. Northern Command (NORTHCOM) and North American Aerospace Defense Command (NORAD). Robinson accepted her new duties during a ceremony at Peterson Air Force Base in Colorado Springs, Colorado. She is replacing Navy Admiral Bill Gortney, who is retiring. Robinson is the first woman to lead one of nine unified U.S. combatant commands. Each command operates under a single commander. The NORTHCOM command includes the U.S. mainland, Alaska, Mexico, Canada, parts of the Caribbean Sea and surrounding waters. NORTHCOM is mainly responsible for civilian support and homeland security while also supervising NORAD, according to the U.S. Defense Department. Both NORTHCOM and NORAD are responsible for protecting U.S. and North American airspace. NORTHCOM was created after the September 11, 2001 terror attacks against the United States.