There are many times in the Fantastic War when you are adjacent to a unit and you want to and can attack, but you don't have to. For example, if you start the turn in an enemies Zone of Control. Also there are times when you're in a Zone of Control but you have a choice of targets. For these cases there is the Allocate Combat command in the Commands menu. You use it just like the Magic Combat command. Select the attacking units from the stack list ([shift] - click for multiples), then select the command from the menu, then click on the enemy stack you want to attack. Of course the defending stack must be adjacent to the attacking stack.
This method allows different units from the same attacking stack to attack more then one defending stack.
