The Fire and Flee Behavior (for Units only) is near the bottom of the Battle Orders menu. It fires for 2 rounds then runs to the back of the battlefield, when they get off the field they retreat to a friendly province (without their commander).

Another way to fire and flee is to set a group of archers with 1 particular commander. Set them to fire and the commander to "Hold, hold, hold, hold, hold, Retreat". They will fire 5 or 6 rounds (sometimes the archers fire even when the commander is in the act of retreating) when the commander is retreating or off the field his units will retreat. If both the commander and units mak it off the field, they will appear together in a nearby friendly province.

Edit: Ignore above; Cherrypie already answered it.

Try splitting your archers into Groups of 10, have the squads all "Fire Rearmost" if that is where your enemy places their mages. Each squad has a chance every time they fire to actually target the rearmost. So multiple squads (4 or 5) have more and more often a chance to target the actual rear instead of 'near' the rear.

I don't have hard numbers; but usually 1 out of 5 squads will actually fire on the rearmost.

[ December 11, 2003, 08:17: Message edited by: Zen ]