Quote Originally Posted by Maltz
Sapping alone doesn't do any good because the arrow towers were killing machines. Siege tower + sapping is the way to go. Using a siege tower to send up troops to capture the arrow towers just beside the sapping point, then one can easily pass the entire army through.
Or just gallop through the sap with cataphracts.

Parthians aren't all that popular and have weak siege, but I've been amazed at how well they can take a town with heavily armored, fast (compared to infantry) cataphracts. They can get out of tower range and into the town quickly. If there are enemy spears about, Persian cavalry horse archers take care of those.

I really need to confirm that post about how cataphracts can use the mace as their alt-attack, which has a bonus against armored troops.