Star Fortresses are major Klingon frontier bases active since the 23rd century.
Located near the borders of the Klingon Empire are major bases known as Star Fortresses. These bases are equipped with communication relay equipment, and have been provided full orbital construction and repair capabilities. Rest and recreation facilities are available for base personnel and visiting ship crews. It acts as the regional headquarters for military assets in the region. Star fortresses have even been built in systems that don't have a single planet that is suitable for colonization. These bases are always supplemented with orbital facilities and defended by in-system defense boats
Star Fortresses have a population that ranges from 50,000 on the low end to 150,000 on the high end, both military personnel and their dependents. Despite being complexes of significant sizes, they are not intended to be permanent bases though a few evolve into such. Due to borders changing as the Empire grows, these bases are usually temporary in nature. When the empire expands beyond the current border, the star fortresses in that region are stripped and abandoned. Defense of the are is delegated to either naval patrols or a more conventional base. Occasionally, the empire will convert a star fortress into a training center, a repair station, or even a Defense Complex. (FASA RPG module: The Klingons: Game Operation Manual)