so you know that for any of these amputations to happen the arm positioning and the strike direction need to be perfect for it to even be possible, which means you're being disingenous by stating it was "common". It wasn't. Did that happen? Yes, but you can't kill someone with a strike on an arm without severing an arteria, though in those times ppl would often die from internal dmg sometimes months after a battle, not during itI am a specialist in medicine, board certified in three fields (emergency medicine, family medicine, dermatology)...I have a black belt in karate (Goju Ryu, 1st dan)...so wrong mate. Be careful with loose statements. Mace/blunt instruments cause crushing injuries - well documented in medical literature. Don't ever say 'ever' unless you were there. Numerous accounts of amputations in medieval combat caused by cutting instruments hitting armor at the joint hinges. Axemen trained to aim at the shoulder pauldron as cutting through the hinge there would incapacitate an opponent - you're pretty useless if you cannot lift your weapon (because the deltoid was severed), and the next fellow with a mace would brain you through your armor plated helmet. And a halberd is pretty much specifically designed to slash at your hinges and then drive the spike through your gap between chest and axilla
I think I'll move on from this.