The base commander is the officer assigned to command a military base. In the United States armed forces, a base commander is generally an O-6 grade officer, meaning Colonel (Army, Air Force, Marines) or Captain (Navy, Coast Guard). However, in certain instances, typically with smaller installations, a base commander may be of a higher or lower rank depending on the size of the installation. In the US Army, a base commander is called a Post Commander. A US Army installation sometimes establishes a base defense operations centers to provide a focus point for defense operations.