At the start of the Close Combat phase, before any blows are struck, both players must choose Unit Strength 10 worth of models (with a minimum of 1 model regardless of Unit Strength) from their unit to form the courageous assault party that will fight in the assault (if the unit numbers less than Unit Strength 10, there is no choice!). Most of the time this will mean ten identical warriors, or at least nine warriors and the unit champion, will form the assault party on each side in the assault, but where there are characters in one or both the units, this selection becomes very important. When it makes a difference, players should roll off to determine which side picks their assault party first.

A character that was not one of the ten models chosen to take part in a building assault cannot be one of the models that step up to replace casualties suffered in the assault, they are far too busy convincing their soldiers to take their place in the assault to get involved themself.