In Khazrak's army, all units with Ambush may use their ability, rather than just half. In addition to these units, Khazrak himself may also be set up in ambush and still be able to sound his brayhorn to launch the attack. If Khazrak is set up in ambush, then any ambushing unit that has an entry point within 12" of Khazrak's entry point may use his Leadership for the Ambush test.