As you might expect, to shoot at an enemy your warriors need to be able to see it. We use two straightforward rules to determine whether or not an enemy can be seen. Firstly, the target enemy unit must lie at least partially within the shooting model's forward arc, just as it would if your shooting model wished to declare a charge (if you need to refresh your memory about forward arcs, see Unit Facing, earlier).
Secondly, the shooting model must be able to trace a line of sight to the target (information on line of sight can be found in General Principles, earlier).