in a custom game its not possible to make the armies play with reinforcements is it?

why doesnt the computer attack both bridges, if there are 2, in a custom game? - I was playing vs 4 comp on a 2 bridge map and they totally avoided the other bridge even after they chased down a router that I had used to lure them it... they only attacked with 2 of the 5 cavalry units at that area and the rest marched back to their formation lines.

I had a few others but I forget at the moment so I'll edit this later to include them