You need to conquer foreign lands either by waging war or intimidating them into surrender.
You might research new technology and forge political alliances, but you do it all in service of one goal: dominance through warfare. Where most grand strategy games have several factors that can determine victory – economic supremacy, scientific progress, or even cultural influence – Total War really has only one win condition, and it’s right there in the title. If Sid Meyer’s Civilization is overbearingly optimistic, then The Creative Assembly’s Total War series is its bleak counterpart.