"The Will of Ashan" - "Heart of Darkness" [2nd campaign, 5th mission]

Kitsune, I killed the assassins and completed the mission without any problems. You don't need to take the girl's troops. Arantir has enough of his own. Besides, there's not much left to fight. Maybe this will help you: http://heroes.ag.ru/heroes5/campaigns/a2/c1/m5/