Can someone explain what happened? (Newbie question)

[daesthai]

My friend and I are both new to Dominions II (this is only our second attempt at playing). I have pangea laying siege to a computer controlled Vanheim fort.

During the turn the Messages indicate there were two battles in the province, one I assume was Vanheim trying unsuccessfully to break the siege, then in the second I stormed the castle. During the fight, I killed all his units and his pretender, and the battle video ends with the message "The armies of Vanheim are routed". However, in the Messages, it says "Our forces were beaten by the defending forces of Vanheim" - even though the numbers show that all of his troops were killed while most of mine survived. And my troops didn't route. Yet I lost the battle. Can someone explain what happened because I don't understand.

Thanks for any help.

~Dae