He went on to become a cornerstone and prestigious figure in Navarre's defense on King Ferdinand II of Aragón's invasion of the kingdom (1512). However, he was captured at Isaba (Roncal) during the failed 1516 expedition against the occupation forces of the Spanish regent Cardinal Cisneros. On 29 May 1518, while prisoner at the Castle of Atienza (Castile), he was offered the apologies of the emperor Charles V should he pledge loyalty to him, in face of which he replied as follows: