On Pedro's arrival at Bordeaux with his three daughters and his son, they were kindly received by the Black Prince, courtesy and kindness to those in misfortune being among the leading characteristics of his nature. Pedro, cruel and ruthless as he was, was a man of great eloquence and insinuating manners, and giving his own version of affairs, he completely won over the prince, who felt himself, moreover, bound in some degree to support him, inasmuch as he, an ally of England, had been dethroned by an army composed partly of English. Pedro made the most magnificent promises to the prince in return for his aid, ceding him the whole of the province of Biscay, and agreeing to pay the British troops engaged in his service when he regained his throne, the Black Prince engaging to pay them in the meantime.
King Edward aided his son by raising an army in England, which sailed for Bordeaux under the command of the prince's brother, John of Gaunt, Duke of Lancaster. Walter formed part of this expedition. The king had issued his writs to him and other barons of the southern counties, and the Black Prince had himself written to ask him to join him, in memory of their former deeds of arms together.
As it was now some years since he had taken the field, Walter did not hesitate, but with thirty retainers, headed by Ralph, joined the army of John of Gaunt.
The Black Prince's first step was to endeavour to recall the Englishmen of the free companies, estimated to amount to at least 30,000 men. The news that he was taking up arms and would himself command the army caused Calverley and the whole of the other English knights to return at once, and 10,000 of the English men-at-arms with the great companies also left Don Henry and marched to Aquitaine. The road led through the territory of the King of Navarre, and the Black Prince advanced 56,000 florins of gold to pay this grasping and treacherous king for the right of passage of the army.
By Christmas, 1366, the preparations were complete, but the severity of the weather delayed the advance for some weeks. Fresh difficulties were encountered with Charles the Bad, of Navarre, who, having obtained the price for the passage, had now opened negotiations with Don Henry, and the governors of the frontier towns refused to allow Sir Hugh Calverley and the free companies, who formed the advance, to pass. These were not, however, the men to stand on ceremony, and without hesitation they attacked and captured the towns, when the King of Navarre at once apologized for his officers, and renewed his engagements. As, however, the Black Prince had received intelligence that he had formed a plan for attacking the English as they passed through the terrible pass of Roncesvalles, he compelled him to accompany the army. The invitation was couched in language which was friendly, but would yet admit of no denial.
On the 17th of February the English army, 30,000 strong, reached the pass. It marched in three divisions, the first commanded by the Duke of Lancaster and Lord Chandos, the second by the Black Prince, the third by the King of Majorca and the Count of Armaguac. The divisions crossed over on different days, for the pass was encumbered by snow and the obstacles were immense. Upon the day when the prince's division were passing a storm burst upon them, and it was with the greatest difficulty that they succeeded in crossing. On the 20th of February, however, all arrived safe on the other side of the Pyrenees. Du Guesclin, who, seeing the storm which was approaching from Aquitaine, had returned to France and levied a French army, was nigh at hand, and kept within a few miles of the English army as it advanced, avoiding an engagement until the arrival of Don Henry, who was marching to join him with the great companies and 60,000 Spanish troops.
Du Guesclin kept up secret communications with the King of Navarre, who was still forced to accompany the English army. The latter accordingly went out from the camp under pretence of hunting and was captured by a detachment of French troops.
On the 1st of April, the Spanish army having joined the French, the Black Prince sent letters to Don Henry, urging him in mild but dignified language to return to obedience, and to resign the throne he had usurped, offering at the same time to act as mediator between him and his brother, and to do all in his power to remove differences and abuses. Henry, confident in his strength, replied haughtily and prepared for battle.
The forces were extremely unequal. The Black Prince had under him 30,000 men; while under Don Henry were 3000 men-at-arms on mail-clad horses, 20,000 men-at-arms on horses not so protected, 6000 light cavalry, 10,000 crossbow-men, and 60,000 foot armed with spear and sword.
The night before the battle the Black Prince lodged in the little village of Navarretta, which had been deserted by its inhabitants. Walter had been his close companion since he started, and occupied the same lodging with him in the village.