US Cavalry Riflemen fire at US Vehicles form German trench
Drive a half-track containing a squad of cavalry riflemen up to an empty German trench, dismount and enter the trench. Cav riflemen will immediately open fire on the half track. Exit the trench and they stop firing, go back into the trench and they think they're German again.
Haven't played the Ardennes Assault campaign for quite a while, but I think this is new behaviour.
Bastogne (from Ardennes Assault)
1 v computer Ardennes Assault Campaign