Been a long time since I've even worried about having legions on a wall waiting for siege towers.

Having about 4-6 units of archers set to "fire at will" and "use fire" seems to be a really good way of keeping too many siege towers from getting too close. If any do, as one of the previous writers suggested, have your infantry off to the side until just before the tower reaches the wall.

If you can get them out there without getting killed, a unit of infantry on the ground "cutting" at the siege tower with swords has been known to bring siege towers crashing to the ground. The drawback is that pieces of it fall on your men, and you will take a few casualties when it happens.

Strength and Honor

Celt Centurion