Warmongers are very strong in numbers, and the "Taunt" ability gives them an additional attack. So, it's more advantageous to upgrade the "Soldier's Luck" skill and hit them with a whip so they move more often, and they will defeat everyone :P :D
In the campaign, I gathered 580 Warmongers and 120 Chieftains. I divided them into 3 groups of 40 Chieftains and hit the 580 with a whip, plus the hero attacked them. It was insane; they moved 2-3 times in one turn! :D