If one of the two sides in conflict thinks that he is going to win (and win undoubtedly), then he will never agree to any compromise. Only if he sees that his victory is in doubt, then he will enter into negotiations.
Look at the today's situation between Israel and the palestinians. They agree to negotiate because each side has got the conclusion that he cannot beat one another undoubtedly.
So we can learn the PR tip: Wish to make your opponent agree to your proposed compromise? First, make him think that you have many options to beat him. Second, make him think that he cannot win undoubtedly.