Edward the Black Prince the party of Montfort, and Chandos won the Battle of Auray (29 September 1364) against the French. As the leaders of the free companies which desolated France were for the most part Englishmen or Gascons, they did not ravage Aquitaine, and the prince was suspected, probably not without cause, of encouraging, or at least of taking no pains to discourage, their proceedings. Accordingly on 14 November 1364 Edward III called upon him to restrain their ravages. In 1365 the free companies, under Sir Hugh Calveley and other leaders, took service with Bertrand du Guesclin, who employed them in 1366 in
Edward the Black Prince differenced royal arms. His younger brother, John of Gaunt, used a similar shield on which the ostrich feathers were ermine. Edward's "shield for peace" is believed to have inspired the badge of three ostrich feathers used by later Princes of Wales. Edward married his cousin, Joan, Countess of Kent (1328–1385), on 10 October 1361. She was the daughter and heiress of Edmund, Earl of Kent, the younger son of King Edward I by his second wife Margaret of France. They had two sons, both born in Aquitaine: From his marriage to Joan, he also became stepfather to her children by