In the middle chivalry (loose rules of wars, feud and honor) required to spare the enemies that surrendered, but you could take them prisoners for ransoms. It w

In the middle chivalry (loose rules of wars, feud and honor) required to spare the enemies that surrendered, but you could take them prisoners for ransoms. It was a totally normal means of financing warfare and profiting from conflicts. Knights were paid using land taxes (not enough) and from loots/randoms (potentially a lot if you were good at it). I guess it was totally usual back then to expect a letter asking for a random for a nobleman to war. If the dude was dead and a the letter a fake, you had no way to know.