More important in its ultimate results was French intervention in Castile. The government of Peter the Cruel had excited the bitter enmity of his subjects, who [Sidenote: War in Castile.] found a champion in the king’s bastard half-brother, Henry of Trastamara. Henry appealed for aid to France, and Charles V. welcomed the opportunity to rid his country of the hated free companies. Bertrand du Guesclin, who had been ransomed from his captors, raised an army among these professional soldiers, and crossed the Pyrenees at the end of 1365. The task of the invaders was facilitated by a general revolt of the Castilians. Henry of Trastamara was crowned king, and Peter fled to Bordeaux to implore English assistance. The Black Prince was conscious that French ascendency in the Spanish peninsula threatened his duchy of Aquitaine, and chivalrous motives impelled him to support a legitimate king against a usurper. Peter made the most lavish promises of pay to his auxiliaries, and the Black Prince became surety for the good faith of his guest. In 1367 all preparations were complete, and the treacherous Charles of Navarre gave a passage through his kingdom to the invaders. Between Najara and Navarrette, not far from the later battle-field of Vittoria, a complete victory was won over the French and Castilian forces. Du Guesclin was once more a captive, Peter the Cruel recovered his crown, and Henry of Trastamara had to seek safety in exile. But Peter proved to be as faithless as he was cruel. He declined to fulfil his promises to allies who seemed to be no longer necessary, and the English prince was in great straits to satisfy the soldiers who had trusted in his surety. To make matters worse the troops were wasted with disease, and the Black Prince himself contracted a fever which remained in his blood and led to his early death. With his temper embittered and his health broken, he led the remnants of his army back to Gascony. His departure was followed by a new revolution in Castile. Henry of Trastamara returned to reclaim the crown, and du Guesclin, whom the Black Prince imprudently allowed to pay a second ransom, once more entered his service. In 1369 the French troops won the battle of Montiel, and in a personal interview which followed Peter was stabbed to the heart by his half-brother. Thus all the fruits of the battle of Najara were lost, and a king was seated in Castile who was pledged to the French alliance.