The sovereign that just wont die

Hello, i've just started playing a new game on a tiny map with a single enemy. I smashed his one and only city with just my sov and a party of peasants (go melting touch go) and now i'm attacking their sov, i'm killing him twice every turn but his essence isn't going down and i think i'm stuck in a continuous loop.

Has anybody else experienced this?

Edit:

Ahah, nevermind i figured out my problem. The battle was just auto-resolving every time and the game wasn't telling me that he was escaping, just playing a death animation after every round, which is what made me thing he was dieing. I set the tactical threshold to 0 and just nuked him with a blizzard. It would be nice to have a message pop-up saying that the enemy turned tail and ran.