Im playing the late era campaign as Byzantium and i am 13 turns into the game. i am assaulting the south-easternmost city of greece using 2 siege towers and a ram. on one tower my spearmen were winning by a lot so i went to watch the combat. then all of a sudden all of the men on the wall started falling down in mass amounts and withing a few seconds i had a routing unit of 40 spearmen. wtf happened?