I was playing a non-mod game, as Ottomans. I had set up a pretty nice little empire already in the south of the Pangea continent, good insfrastructure, etc. I met the French to the north and they were weaklings, so after extorting their entire treasury, I declared war

. I captured one city (not even the capital, but the other city that they had) and I got a message that the French have been destroyed. I didn't think of it too much. Just figured "all right now I can expand further north".
I meet the Egyptians, they're a bit stronger than the French, and we are on-par militarily and technologically. One of their cities falls to me, and suddenly the other 5 cities they have are reduced to rubble. That's when I start wondering "what's up?", because I was looking forward to another nice little war.
So after that, I send a group of soldiers (I forget what kind they were - Archers, I think?) further north, and I encounter the Japanese. Again, war. For two reasons this time: First and foremost, to gain territory; Secondary motive is to see if it happens again. It does. Kyoto falls, and all of Japan is nothing.
So I give it another shot, with the Scandinavians. Again, one city falls, so does the empire. I'm pretty angry by now because I mean it's not even the Middle Ages yet and already I mowed down 4 of the 7 civilizations, with just a flick of the finger. So, angry, I check the Victory Status screen... I find out that it's one of those games where if one city falls the entire civ falls (Elimination, I think it's called?). I go back to the New Game screen and check the options, and I did accidentally check that box for that kind of game. I smack myself in the forehead while mourning the uselessness of my Ottoman Empire's magnificent progress.