I'm not sure whether this is a bug or not. I'm on my 7th or 8th game since entering the beta, and I haven't seen this before. Now in this game I've seen it twice. I have an army of 7 units. I conquer an enemy town, and 4 of my units are placed in the town, with 3 left outside it. The second time, my 4 strongest units were put in the town, leaving my 3 weakest units to fend off an attack by themselves after the initial battle for the town. Has anyone else seen this? Unfortunately I don't have a saved game from just before the attack on the town, so I don't know if it's reproducible.