Commander..You are allowed 1 main base,,your base and 3 annexed bases, these annexed bases are "occupies" that you can recieve a certain % of thier production of either Fuel or ammo..You may  have/hold as many occupies as you like. but bear in mind that occupies are often hit  as a source of Resources by other players,,if they see that a base is occupied, then they know that that player is in-active and can be a good source of resources..Some player will acutually occupy a base and load it up with defense as a means to PVP..Always a good idea to recon first any base you desire to hit