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.