If the attacker wins, the defender must take a Break test. Note that units garrisoning buildings are always considered steadfast.
If the defender fails the Break test, then the garrison unit is placed outside, directly opposite the assaulting unit, as described for a unit abandoning a building. If this cannot be done, place it as near as possible to this position. It then makes its fleeing move as normal.
The attacker cannot pursue, but can enter the building if its controlling player wishes (and is of a troop type that is permitted to enter the building). If the unit does not enter the building it is moved directly backwards 1".