If I choose just one war game?

Tough question because you don

Thanks for the answers. :-)

I should say I am looking for "one night, pseudo wargame". What I want is a game that can be played 2~3 hours. Also I am looking for war+something from the game. I think that war is not just battle. So game should have something more than just battle. For example, diplomacy.

I think that Mare Nostrum is well matched what I want. But if you have any other recommendation, please let me know.