Someone with complete power over a place "rules" it. This is usually a king, queen, emperor, etc.
In modern days, you don't say that a president or prime minister "rules" the country that they're leaders of. That's because presidents and prime ministers don't have complete control; they have to follow certain rules and laws, and the citizens of the country can have them replaced.
Because of this, you should remember these phrases:
ruled the kingdom
ruled the empire
ruled the land
governs the nation
leads the country