First strike Retreat

Hello,
the french will attack my english unit. After (Wellington) use the card „first strike“ i threw a flag, so that the french unit has to retreat. Can this french unit now make a range combat against the first strike unit or another english unit, because ithe french umit was activated but had alteady not fighting?

Interesting question not directly addressed by the rules, however the spirit of the retreat rule is that a unit which retreats is precluded from combat in that turn, by virtue of being disordered by its forced movement. The First Strike card explicitly states "If the opponent’s (in this case the player whose turn it is) unit is neither eliminated nor retreats it may then battle as originally ordered. " There is no suggestion that a unit forced to retreat after FS is allowed to start shooting instead of melee "as originally ordered". That French unit is out of luck I'm afraid.