Diagram: Crossfire. A Dark Eldar squad is falling back but a Space Marine is inside their fall back corridor. He is 6" from the nearest Dark Eldar, so if the warriors roll 6 or more on 2D6 they will be destroyed. They roll 6, and are killed in the lethal crossfire.
Units forced to withdraw through enemy units will be caught in a deadly crossfire and destroyed or irrevocably scattered. If a unit is withdrawing towards the enemy measure the distance to the nearest enemy model within the fall back 'corridor' before rolling to see how far the unit falls back. If the distance rolled takes the unit up to or past the enemy model the unit is destroyed.
Note that only models from units that have not fought in close combat that turn can be used for crossfire purposes.
Errata — Chapter Approved: Main Rules Clarifications (v2.0): The only circumstances in which crossfire does not destroy a falling back enemy unit are when the unit's fall back path passes through:
- a unit that forced it to fall back in close combat;
- a unit which is falling back itself or which has performed a sweeping advance or consolidate earlier in the same assault phase;
- a unit which is pinned;
- a unit which is separated from them by impassable terrain (in this case, the falling back unit would divert around the impassable terrain anyway).