Army retreated for no reason

[13Foxtrot]

I had an army that was defeated by a larger force. The same day they were defeated I had another superior army at full morale show up and automatically retreat without a fight. Apparently it retreated based on the other defeated army retreating. I don't think that should have happened. Using 1.1

 

[King]

If they arrive just as the battle was lost then yes they are carried back in the rout.