Base
A base, or military base, is similar to a city except it covers the whole world. All military buildings on the same world are part of the same base.
A military headquarters is the basis of any base, it is required before any other military buildings can be constructed.
Claim Defense
The primary purpose of a base is to protect the empire's claim over a world. While a military headquarters exist on a world the claim cannot be stolen.
Meanwhile the military headquarters cannot be destroyed while and other military buildings exist on the world.
Base Population
The population of a base live in military barracks, they function as workers for military buildings that require workers, otherwise they are soldiers that protect the world.
Base Buildings
All military buildings on the world belongs to the base. Power plants that are not part of a city will be part of the base and therefore be considered military buildings.