Attached to the English side in the conflict, he was made Count of Bigorre by Edward III of England, and was also a founder and the fourth Knight of the Garter in 1348.
[2] He played a decisive role as a cavalry leader under Edward, the Black Prince in the Battle of Poitiers in 1356, with de Buch leading a flanking move against the French that resulted in the capture of the king of France, (John II), as well as many of his nobles.
[3][4] In 1364, he commanded the forces of Charles II of Navarre in Normandy, where he was defeated and captured by Bertrand du Guesclin at Cocherel.
The Captal spent the remainder of his life as a prisoner at the Temple in Paris, because Charles V believed him too dangerous to ransom back to the English.
Froissart gives an account of the Captal de Buch's chivalry and courage at the time of the peasant uprising in 1358 called the Jacquerie (see link).