He made his name famous in 1217 when, for six weeks, he defended the castle of Montgrenier against the onslaught of Simon de Montfort, 5th Earl of Leicester. That same year, he distinguished himself at the siege of Toulouse. In 1220, he assisted his father in the recapture of Lavaur and Puylaurens and was instrumental in helping his father retake his lost dominions. The resumption of Mirepoix wasn't accomplished until his own reign, however.