There he took part in a sequence of raids, sieges, and counter-measures against the French, with both notable successes and failures. The latter were compounded by his apparent inability to work alongside the famed soldier Sir John Chandos, who, although head of the King's forces there, was far below Pembroke in rank. He was, however, far above Pembroke in ability, and his subsequent death led to even more problems for Pembroke in France. A couple of years later, the earl was summoned to parliament and returned to England. There, perhaps exasperated by the political failures of the king's ecclesiastical ministers, he was responsible for forcing them from power and being replaced by laymen. Pembroke was soon to return to France again, for what was to be the last time. In 1372 he set off with a small fleet, intending to raise a new army once in Aquitaine. However, his arrival had been anticipated by the Castilian navy (whose kingdom was then allied to France). Pembroke, outnumbered and outgunned, was forced to fight at the Battle of La Rochelle, where he went down to a crushing defeat. Captured and taken to Castile, he was imprisoned in harsh conditions. It took a further three years for a large ransom to be negotiated, but in 1375, he was finally released. Returning to England through France, he was taken ill near Paris and died before reaching home. He was about 28 years old; his wife survived him, as did a son, born in 1372, whom Pembroke had never seen. Also named John, he would eventually inherit the earldom. Pembroke was buried in Hereford in spring 1375.