The son and heir of Henry, 3rd Earl of Lancaster, and Maud Chaworth, Grosmont became one of King Edward III's most trusted captains in the early phases of the Hundred Years' War and distinguished himself with victory in the Battle of Auberoche. A late 14th-century chronicler described him as "one of the best warriors in the world", while Froissart calls him "a good knight" and a "valiant lord, wise and imaginative". Thomas Grey, writing a few years after Grosmont, called the duke "wise, full of glory, and valiant, and in his youth eager for honour and feats of arms, and before his death, a fiercely devout Christian". Several modern historians have agreed with this assessment; Margaret Wade Labarge, for example, has called him "one of the outstanding figures of a reign which abounded in colourful chivalric personalities". Grosmont, made Earl of Derby in 1337, Lancaster on his father's death in 1345 and a founding member and the second Knight of the Order of the Garter three years later. In 1351 he was created Duke of Lancaster, only the second such creation and the first non-royal dukedom. He was the wealthiest and most powerful peer of the realm, but, comments Janet Coleman, he was no scholar, something Grosmont readily admits; while his discussion of things religious is broad, imaginative and wide-ranging, he himself points out that he deliberately avoids "profound matters".
