Lost battle although enough moral?

[yxcv]

Hi, i'm yxcvasdf at worl 261.
I don't understand what happened here: You attacked SpSmkd (tralala) in Province 1. 29.03.2015 21:20.
Could someone pleasr explain that to me?

[Angela]

Hi yxcvasdf,

Too many swordsmen participated in the fortress siege, more swordsmen and battering rams could help you to destroy the fortress faster. Your army's morale dropped below 50 and it fled from the battlefield before destroying the fortress. The swordsmen, battering rams and cavalry fled at 37 morale, the archer a little later - at 38 morale points.