I think the computer plays this exploit. I have often seen factions send off huge armies which don't even seem to be trying to get there and would be so very late that they don't have much chance of getting there to take a city unless 5 other armies get defeated. I just had to destroy an impressively powerful French stack of "ex Crusaders" who never got close to getting out of France. The stack had many mercenary spears and crusader sergeants and 5 crusader knights and a mounted sarg and 3 mailed knights. The only weak units were 3 peasant crossbowmen. Having a 7 star general and each unit having a chevron resulted in me losing 600 men in a close battle in which my 61-year old king performed a few suicidal charges. However, I can not recall ever seeing an AI faction send more than one Crusader Army. Has anyone else?