At Agincourt the prisoners that were executed were all noblemen or landed knights. The custom was for these prisoners to be taken, because they could be ransomed back to their wealthy families. It was a shocking event because it broke the conventions of the times.

It would have been very unlikely that common men would have ever been taken prisoner. They'd have just been slaughtered on the battlefield, if they did not run away.

operative term being if they did not run away I think.

At any rate the breaking the conventions of the times is the thing that draws a mention, in the same way that a man biting a dog does.

Allegedly the same happened at Aljubarrota; prisoners were killed to let more soldiers fight on the front line.

What an amazing world-changing battle! Brother versus brother, English longbows versus French heavy cavalry (again) . . . Try to imagine a world without a Henry the Navigator.

https://en.wikipedia.org/wiki/Battle_of_Aljubarrota

I was not aware the Castillan forces were commanded by the brother of Nuno Álvares Pereira. He's less known nationally than the mythic Brites fe Almeida.

Why don't the history teachers drop these snippets during classes?