I was playing as HRE and got attacked by the Danish king and his 6 sons/uncles along with some viking/urban militia. The map was one with 2 bridges, each one was held by feudal sergeants, supported by FMAA and 2 crossbow units. I had 1 unit of 20 royal knights. The Danish attacked me on one bridge, banners high in full charge. All of their troops charged my single Feudal sergeants unit and were involved in close combat with them. That gave me time to walk my knights on the other side of the bridge and charge them from behind into the Danish units. Result: the Danish were all killed and wiped out... now what I wonder: I play on normal, is it usual that the AI does such rather stupid things on this difficulty?