In 1643 he acted as commissary-resident for the three legations held by Cardinal Antonio Barberini over regions in which he did not reside - effectively operating as the cardinal's representative in those regions when the cardinal was not there. He was also sent by the pope as legate to Lombardy during the First War of Castro to reach a peace agreement with the Dukes of Parma after the pope renounced the peace agreement negotiated by Cardinal Bernardino Spada. He was then named Protonotary Apostolic at the Datary.