The Ministry of War is responsible for all matters of warfare within a city. The sole exception to this is enlistment, which any citizen may perform.
It is up to the Minister and his aides to capture territory, and plant the glorious flag of their homeland upon foreign shores. Expansion means prosperity, while contraction can mean poverty. Of course, a balance has to be struck between ploys to gain territory, and the cost of troops. No nation can afford to fight forever.