Quote Originally Posted by Beelzebub
There's some bugs with sieges. I had a garisson in my selucid city that was under siege by a lot of Macedonians. I sent some Phalanx units to the north side of the city and then did a sortie so I could bring them into the battle as reinforcements, and then move them inside the city to reinforce the garisson. I didn't want to fight the macedonians in the field cuz they had a ton of cavalry and I thought my mostly Infantry force would get slaughtered in the field.

When I started the battle I got a message that my reinforcements were delayed (they never came), so I did some skirmishing with my archers and slingers. Ended up killing about 150 Macedonians while taking about 80 casualties so it counted as a victory when the timer expired. When I got back to the strategy map, all 3 Macedonian armies (over 1000) troops had disbanded cuz I had a slight victory in some inconsequential skirmishing..
Are you sure they disbanded? Usually they move back into their territory, even if that´s on the other end of the map, you don´t always get to see that, but it might be the case, if not, then it should be a bug.