There wasn't a single "world power" then, and there normally isn't. That's what is so odd about the present situation. Normally there's a bunch of rivals squaring up to each other, or makin alliances, or competing.

That's why to find anything comparable to this where there's only one power really in the business you have to go back to Roman times, when, within what was effectively a whole world, there was only on player that counted. (And up the other end of the Old World, you could say the same of China.)