In my previous article on the geometry of empires, I considered two essential strategies for organizing the defense of a territory. In one, troops were positioned along the border, ready to intercept enemies but spread thin. In the other, a single, centrally-located force was powerful but slow to respond. These are extreme approaches, though, lying at the ends of a spectrum filled with intermediate strategies.
The pre-modern state aims to defend its borders against enemies. The size of its territory, though, has profound implications for how it can do this; which may in turn influence how that state develops--whether, in particular, it seeks aggressive expansion.