These measures would have troubled Pedro little had it not been that France groaned under the great companies, and the French king and the pontiff at once entered into negotiations with them to support Henry in his war against his brother. It was necessary that a leader in whom the companies should have confidence should be chosen, and Du Guesclin, still a prisoner of Chandos, who had captured him at Auray, was selected, and the pope, the King of France, and Don Henry, paid between them the 100,000 francs demanded for his ransom. Du Guesclin on his release negotiated with the leaders of the great companies, and as the pope and king promised them large gratuities they agreed to march upon Spain. They were joined by a great number of French knights and men-at-arms.

The expedition was under the nominal command of John of Bourbon, but the real guidance was in the hands of Du Guesclin. As the army marched past Avignon they worked upon the terrors of the pope until he paid them 200,000 francs in gold. France was filled with joy at the prospect of a riddance of the free companies which had so long been a prey upon them. They were, too, eager to avenge upon the cruel King of Spain the murder of his queen, who was a princess of France. The same feeling animated the people of Aquitaine, and Calverley, D'Ambrecicourt, Sir Walter Hewitt, Sir John Devereux, Sir John Neville, and several other distinguished knights, with a large train of men-at-arms, joined the adventurers. The great army moved through Arragon, whose king in every way facilitated their progress. As they entered Castile the whole people declared in favour of Henry, and Pedro, deserted by all, fled to Bordeaux and besought aid from the Prince of Wales.