Have a map of the ancient world and you move armies and characters around and take cities, etc. There would be the high level "strat" map of the Mediterran, Middle East, North Africa, Greece, or wherever the campaign takes place. You'd drop into RTS level to play out the moves. So, if you want to take a province, you'd drop down to the level of a skirmish map and play it out against the AI. If you win the match, you're given the province.