If previous sectors acquired by negotiation:
Frathia, my pride. I would love to show you around longer, however I have a war to attend to. And I could really do with a few things.
If at least one sector taken by force:
Hyena! You come to feast on the dead? I am already losing in a war, and you want to take a piece of cake, yes? Can't we make some peaceful negotiations rather than fighting?
Why are you attacking me? I am no threat to you!