Quote Originally Posted by bobbin View Post
And these are more feasible frontiers how exactly?
I'd argue that the Roman handbook regarding borders would tell you that rivers make the finest boundaries of empire. The Rhine and Danube clearly. In the east against the Parthians and Sassanids the border shifted more, but was generally based around the Euphrates region. In Africa there were no major rivers but the Atlas mountains and the Sahara were natural boundary markers. In Britain they eventually built a wall although its uses and purpose are arguable. Also as long as the capital of the empire was Rome, the Crimea was somewhat far away and as long as the native Bosporans were friendly and willing to trade their grain, there would be no reason to incorporate them into the empire unless they were in danger of being deposed by native revolt or foreign invasion.