Who is Constable du Guesclin from Strategy and what is their importance?

This French Great Captain made as his main contribution the riddance of the English from "predominantly" French territory. His methods consisted of an introduction to elements of guerilla war tactics combined with showing the importance of attacking supply lines instead of, or as much as, assaulting opposing troops. He consistently refused to engage well fortified garrisons just as Belisarius had also refused to do. "No attack without surprise", was a phrase for which he is still famous.