I have been having a lot of troubles trying to bring units through a gate while seiging a city. For example, I had my Cavalry enter the gate first to meet the defenders and tried to move my infantry in after to support them. For some reason my infantry not only did NOT go through the gate, but they (for some unknown reason) fell back to my original front lines! This caused my attacking force to become split and I lost many casualties in my cav unit that could have been avoided. It seems like any time I bring a unit to the gate when there is already a unit entering the city, the units become confused and fall back to the front lines instead of waiting to go through the gate like they should.