I found that if you click the option button in the top left corner of the screen after the AI attacks you (in the tactical battle screen), and press escape to exit the screen, the battle ends, the AI's turn ends, and it becomes your turn again.  You can use this to avoid any fight you don't want to have with the AI.  Once this happens though, the game will lock up where you will be unable to go to your next move.  You can click end turn, but your turn starts again, and the button becomes grayed out.  At this point you will be unable to attack anyone, or end the turn.  Even reloading a save will not fix the problem.  The only way I have found to correct this is to save the game, and close out of the game completely, then open the game again, and load the game to continue.