You have made peace with ...???

[DutchLuke]

Finally, I was attacking Darius with the full strength of my Egyptian army, I was about to take Persepolis, and then.. next turn ... "You have made peace with Darius"

I did not ask for that, I was about to annex his capital!!
Does anyone have an idea what happened to me?

I had 4 allied city-states, and 2 pacts of cooperations with other civs.
I played on chieftain level.

 

[bsliv]

Happened to me twice while fighting Japan and then Iriquois. Not to mention that this is coupled with the endless peace bug and totally ruined the game.

At first I thought it was a Wonder thing I didn't know of, but after some civilopedia, turned out to be another bug.