At 7th level, when a foehammer succeeds at a bull rush combat maneuver, he can make a trip combat maneuver at the end of the bull rush. If he does not move with the target, the force of his blow may still trip his foe, but he takes a –5 penalty on the combat maneuver check to trip.
At 15th level, any creature a foehammer successfully bull rushes is automatically knocked prone at the end of the bull rush. This ability replaces armor training 2 and 4.