Soon again two armies were in the field, that of King Henry, raised to defend his new dominions, and that of the Prince of Wales, gathered to replace the fugitive Don Pedro upon the throne. With the latter was the White Company, which had aided to drive Pedro from his seat and was now equally ready to replace him there. These bold lancers and archers fought for their own hands, with little care whose cause they backed. It was through the valley of Roncesvalles, that celebrated pass which was associated with the name of the famous Roland, the chief knight of French romance, that the army of the Black Prince made its way into Spain. Calverley, who was not willing to fight against his liege lord, joined him with his lances, King Henry generously consenting. Du Guesclin, a veteran in the art of war, advised the Castilian king to employ a Fabian policy, harassing the invaders by skirmishes, drawing them deep into the country, and wearing them out with fatigue and hunger. He frankly told him that his men could not face in a pitched battle the English veterans, led by such a soldier as the Black Prince. But the policy suggested would have been hazardous in Castile, divided as it was between two parties. Henry remembered that his rival had lost the kingdom through not daring to risk a battle, and he determined to fight for his throne, trusting his cause to Providence and the strength of his arms. It was in the month of April, 1367, that the two armies came face to face on a broad plain. They were fairly matched in numbers, and as day broke both marched resolutely to the encounter, amid opposing shouts of "King Henry for Castile" and "St. George and Guyenne." It was a hard, fierce, bitter struggle that followed, in which the onset of Du Guesclin was so impetuous as for a moment to break the English line. But the end was at hand when the Castilian cavalry broke in panic before the charge of an English squadron, which turned Du Guesclin’s battalion and took it in flank. The Captal de Buch at the same time fell on the flank of the Castilian vanguard. Thus beset and surrounded, the French and Spanish men-at-arms desperately sought to hold their own against much superior numbers. King Henry fought valiantly, and called on all to rally round his standard. But at length the banner fell, the disorder grew general, the ranks broke, and knights and foot-soldiers joined in a tumultuous retreat.