Philibert was destined for the church, and was educated at the college of Pau, in Béarn. He refused the ecclesiastical life, however, and joined the army of Prince Thomas of Savoy, then in 1643 besieging Trino in Piedmont. He afterwards served under his elder half-brother, Antoine, marshal de Gramont, and the prince de Condé. He was present at the battles of Freiburg and Nördlingen, and served with distinction in Spain and Flanders in 1647. In 1654 he fought at Arras where Turenne relieved the town besieged by the Spanish.