Age of Empires is an RTS game. I'm not quite sure how Civilization is arcady, it is a turn based strategy game.
Total War games are kind of hybrids, turn based strategy with real time battles. Although I wouldn't classify those battles as RTS, as you aren't building units and managing resources in combat.
I've never played Cossacks either, but if you are building, managing resources, and armies all in real time, it would be a RTS game more like Age of Empires or Stronghold.
edit: Bart beat me to it, but you can have an RTS game with more focus on the armies and troop movement. It seems like Cossacks might fit that mold.