Ooops! Had to re-do this post because I accidentally deleted it by hitting Ctrl-Z. Stupid blogger!
Before you can fire your unit's weapons at the enemy, you must be able to see them. This section covers the basics of model/unit visibility and target selection.
Any enemy unit that is in Line Of Sight to the firing unit's leader may be targeted for shooting.
An enemy unit is considered to be in Line of Sight if any of its individual models are visible to your unit's leader.
I See ‘Em Sarge!
If none of an enemy unit's models are visible to your unit's leader, but are visible to one or more of the other models in your unit, then you may still be able to target that enemy unit. It will, however, be more difficult. Roll a Ld check for your unit.
If the Ld check is passed, the trooper who saw the enemy shouted loud enough for his unit leader to hear him. That enemy unit may then be targeted as normal. If the Ld check is failed, then the enemy unit may not be targeted that turn.
Note that this roll, passed or failed, does not commit you to firing at that enemy unit. It only determines whether the enemy unit can be targeted. Your unit will later select its final target(s) from amongst all visible enemy units when it rolls it's ranged attacks.
Always Take The Easiest Shot
If 2 or more models in a targeted unit have different levels of visibility, then the most visible model in that unit will determine the entire unit's visibility. So long as that model is in LoS of the unit doing the targeting.
Model Visibility Levels
There are 5 basic levels of model visibility, from most most visible to least visible.
If an enemy model is considered to be in the clear, then you can see, and target, that model's unit anywhere on the table. So long as the model is within the range of your unit's weapons.
If a clear model's unit has performed a Get Down! action, then the unit will be considered to be obscured, rather than clear.
Obscured targets are more difficult, but not impossible, to see. An Obscured model may be targeted normally, though it will be harder to hit with ranged weapons than a visible model.
If, however, an obscured model's unit has performed a Get Down! action, then the unit will be considered to be concealed, rather than obscured.
Obscured units add +1 to their starting Ev.
Concealed models cannot be seen or targeted at all. Unless they have moved At The Double, performed an Open Fire action, or are within a unit's Awareness Range.
If a concealed model's unit has performed a Get Down! action, then that unit will be considered to be hidden, rather than concealed.
Concealed units add +1 to their starting Ev.
A hidden model is one which is completely behind a solid wall, tall hill, or other non-moveable terrain feature.
To determine whether a model (or its base) is hidden, bend down and look from just behind the head of your unit's models, out towards the enemy model. If you can physically see the enemy model, then it is not hidden. If you can't see the model at all, then it is hidden.
Hidden unit cannot be targeted unless they are within your unit's Awareness Range. Even then, they will be harder to hit than a unit which is simply concealed.
Hidden units add +2 to their starting Ev.
Real life battlefields are not as perfectly flat as a gaming table. Normally, the members of a unit will use the small imperfections in the terrain to their advantage. Crouching low, and using every little rise or dip in the field to conceal themselves.
Sometimes though, a unit must move quickly. Trading careful, stealthy movement for speed. The terrain that they're crossing might also be paved, hard-packed, or otherwise difficult to hide in. In which case they will count as Exposed.
The Awareness Range of a firing unit will be doubled when targeting an Exposed unit.
Splitting A Unit’s Fire
A unit may split its fire amongst any any visible enemy units. When rolling To-Hit, simply declare which of your models are firing at the current target. Each model in your unit may only fire at a single target during the same action.
You don't have to declare all of your unit's targets in advance, but once you have rolled to hit with all of your declared models at a particular enemy unit, you may not target that enemy unit again during the same action. If you have already fired at all of your unit's visible targets, and you still have models left in your unit which have not yet fired, then those models will not be able to shoot for the remainder of that action.
Special Rule: TacCom
If a unit has been provided with the proper communications gear, it can share targeting information with the other squads in its own Strike Force.
When the leader model of a unit with the TacCom special rule targets an enemy unit, you may place a TacCom marker on that enemy unit in leu of the leader's normal shooting.
On a successful Ld check, any other friendly units which also have the TacCom rule may double their Awareness Range when targeting the marked unit.
All active TacCom markers are automatically removed at the Beginning of the Reaction Phase.
Special Rule: SquadCom
In some units, every trooper is able to communicate with their leader via a helmet link, telepathy, or other means. This makes it much easier to get the leader's attention during the heat of battle.
A unit with the SquadCom special rule does not require a Ld check in order target an enemy unit that is visible to a unit member, but not the unit's leader.
Target Model, Firing Model
For the remainder of the Shooting rules, 'Target Model' or 'Target' shall describe any model, in an opposing unit, which a player's unit is currently attempting to either target, or actually shoot with its weapons.
By the same token, 'Firing Model' or 'Firer’ shall refer to any model in a unit which is attempting to either target, or shoot, a particular enemy model.
When the shooting rules simply refer to a 'model', this should be understood to apply to either a Target Model, or a Firing Model, equally.