After the Catalan revolt of 1640, Philip IV tried to win over Aragon to raise money and men for the new war front. One of the steps taken towards this end was to bring the Prince Balthasar Charles to be sworn as crown prince of the Kingdom of Aragón. The oath was held on 20 August 1645, when the prince was sixteen years old, in the Cathedral of the Savior, Zaragoza. This titled him as Prince of Gerona, Governor General of Aragon, Duke of Montblanc, Count of Cervera and Lord of the City of Balaguer. Meanwhile, on 13 November of that year, Balthasar Charles was also sworn as heir to the Kingdom of Valencia.