ok, so response fire.
If you are playing in a battle in which you are taking turns as to whos turn it is to move and fire. And you can consider a turn to have happened once every player has had a chance to move and fire. Then it makes sense that if a unit of one of the first players did not take an action then it would be able to have a response action instead. BUT, if an opportunity arises in which a player has not had his turn and would like to make a response action, is he allowed to make a response action? Because technically, he has not made the decision yet as to whether he will do something or not.
This problem does not really seem to come up in real battles, but with forum battle s it seems to be a pretty big issue.