Five of the uniformed services make up the U.S. Armed Forces, four of which are within the U.S. Department of Defense. The Coast Guard is part of the Department of Homeland Security and has both military and law enforcement duties. Title 14 states that the Coast Guard is part of the military at all times, making it the only branch of the military outside the Department of Defense. During a declared state of war, however, the President or Congress may direct that the Coast Guard operate as part of the Navy. The U.S. Public Health Service Commissioned Corps, along with the NOAA Commissioned Corps, operate under military rules with the exception of the applicability of the Uniform Code of Military Justice, to which they are subject only when militarized by executive order or while detailed to any component of the armed forces.
Reserve components of the United States Armed Forces are all members of the military. The National Guard is an additional reserve military component of the Army and Air Force, respectively, and is composed of organized state National Guard militia units, which operate under Title 32 and under state authority as the Army National Guard and Air National Guard. The National Guard was first formed in the Colony of Virginia in 1607 and is the oldest uniformed military force founded in the New World. The National Guard can also be mobilized by the President to operate under Federal authority through Title 10. When acting under federal direction, the National Guard of the United States is managed by the National Guard Bureau, which is a joint Army and Air Force activity under the Department of Defense, with a 4-star general from the Army or Air Force appointed as its top leader. However, in Federal service command and control of National Guard organizations will fall under the designated Geographic or Functional Combatant Commander. The National Guard of the United States serves as a reserve component for both the Army and the Air Force and can be called up for federal active duty in times of war or national emergencies.