Medieval English kings were not nice people. Edward III (1312–1377), in particular, used his son the Black Prince to wage a form of warfare called chevauchée, which consisted of killing and burning everyone and everything that could be reached by fast-moving raiders. The object was twofold. One was to destroy an opponent's logistics base and discourage supporters. The other was to bait the opponent into leaving a good defensive position and coming out into the open, where he could be attacked; a noble needed strong nerves and a stony heart to stay behind walls while his subjects were slaughtered and...