For example, at Agincourt, apparently many French POWs were killed in retaliation to the French killing non-combatants during/prior to the battle. I've also heard that POWs would sometimes be executed simply because there was nothing to do with them. The army didn't want to deal with a potential uprising, or escapees reporting their movements/position to the enemy.
If an army in the medieval/ancient era were to kill hundreds/thousands of POWs or captives, how would this be done? Was it even done at all? I know the Aztecs would sacrifice captives. But what about European and Asian armies?
Thanks.
The prisoners at Agincourt were not killed in retaliation to the attack on the baggage train (which may not have been very significant to begin with). The order to execute the prisoners was given when the English either saw or thought they saw that the French were massing for another attack. Henry V feared being caught between a fresh French advance and an uprising from the prisoners. Therefore, he ordered the slaughter of the captives before anything could happen. When the French failed to sustain any fresh assaults, the killing stopped. Contrary to some modern perspectives on the battle, this was not considered outside the customs of war in the day and similar events took place in other battles.
The killings were carried out in several different ways. For one, all prisoners would have been disarmed and stripped of their helmets. Some may have had their hands bound (a few artistic depictions of prisoners indicate this), but it's doubtful that there would have been any organized attempt at shackling every single prisoner. We know from one account by a surviving French soldier that there was some effort to separate the large number of prisoners. The soldier wrote that he was locked up with several other prisoners in a local shed or farmhouse, which was then set on fire when the order to execute prisoners was given. Most of the captives were probably killed with hand weapons. Without helmets, it would be fairly trivial to dispatch a man in a single blow of a sword, dagger, or hammer. Other French accounts describing the aftermath of the battle indicate that many corpses had head or face wounds, indicating that they had been taken prisoner and subsequently executed.