Quote Originally Posted by Knight of the Temple
And in case you didn't know, units on 'Fire At Will' will not turn to fire at anything directly behind them.
Correct. As far as I know there are only two ways to stop a missile unit from firing if a target is within range: (1) move the unit physically out of range of any target, and (2) make the unit face away from all possible targets.

The latter is faster as well as safer (your missiles are close at hand if they are needed).

This knowledge may come in handy if you want to save ammunition at some stage (e.g. during a lengthy battle).