Edward the Black Prince compelling Peter of Castile to flee from his kingdom, and in setting up his bastard brother, Henry of Trastámara, as king in his stead. Peter, who was in alliance with Edward III, sent messengers to the Black Prince asking his help, and on receiving a gracious answer at Corunna, set out at once, and arrived at Bayonne with his son and his three daughters. The prince met him at Capbreton, and rode with him to Bordeaux. Many of the prince's lords, both English and Gascon, were unwilling that he should espouse Peter's cause, but he declared that it was not
Edward the Black Prince were traitors. On the morning of the 3 April the prince's army marched from Navarrete, and all dismounted while they were yet some distance from Henry's army. The vanguard, in which were three thousand men-at-arms, both English and Bretons, was led by Lancaster, Chandos, Calveley, and Clisson; the right division was commanded by Armagnac and other Gascon lords; the left, in which some German mercenaries marched with the Gascons, by the Jean, Captal de Buch and the Count of Foix; and the rear or main battle by the prince, with three thousand lances, and with the prince was Peter and,