Phobos

A miniature colony that is entirely populated by military personnel. Phobos was colonized long after Mars, its very small size and irregular shape making it ill suited to any such efforts. The inside of the moon is hollowed out in order to make room for a large hangar bay and multipurpose military facility in its interior, with entrances set deeply into its craters and spaced across its surface. This humongous military complex is usually referred to as Phobos Base. Phobos Base is used as a staging area for military operations, a garrison to defend the planet it orbits, and a launch site for interplanetary ballistic missiles. Although its actual population hovers around one and a half million, there are over ten million troops officially stationed at Phobos Base, with most of them assigned to space patrols at any given time.