As the title says, I was in an AI territory and he declared war, so I was moved out. And I ended up in the little valley with the final part of the Epic quest with just the big dragon, whose name I forget, to fight. Unfortunately, my army was not great - about 600 hp total, so I lost that battle. I had not done any of the precursors of the quest - the gate was still closed, and I had not revealed the map for that area either

I suspect that this was a very rare thing to happen. The valley looked to be 1 square less far away than where I expected to be moved. I don't know if it is possible to flag a tile as "do not move here after war declared" or even if it would be worth it.

Anyway apart from a few random crashes, the game is great. Time to try the next game on Ridiculous.