Editing Warhammer 40,000/Tactics/Kill Team(8E) Guide and FAQ (section)

===Pile In/Choosing models to fight===
A model can make a Pile in move of up to 3" towards the nearest enemy model when it is chosen to fight. Pile in moves happen before the model resolves any attacks.
For a model to be eligible to be chosen to fight, during the fight phase, at least one of these conditions has to be fullfilled:

*The model charged successfully.
*The model was charged successfully.
*The model is within 1" of an enemy model.
*The model is given the ability to fight through the use of an ability or a tactic.

This means that it is possible for a model to be chosen to fight later in the fight phase, due to an enemy model piling in/consolidating into it. This also means that a model can be chosen to fight and make a pile in move, even if there are no enemy models within 1" of them, as long as one of the first two conditions was fullfilled. This can happen when an enemy model, that was within 1" of your model, was killed before you choose this model to fight.