At the battle of Poitiers the Black Prince was able to successfully defeat the French forces there in addition to capturing the King of France, John II.

What I don’t understand is why the English decided to ransom the king back to the French. Surely with the French king they could demand the surrender of the French as a whole. It’s not like the English had done poorly prior either to warrant the French believing this was just a fluke. The English had made gains in Brittany, Calais and Gascony.

I’m assuming that the situation wasn’t as simple as I’m making it out to be, but that’s why I’m here to ask you guys.