House of Sforza
In February 1621 Ludovisi's brother, Alessandro Ludovisi, was elected to the papal throne as Pope Gregory XV. A month later, on 13 March 1621, Ludovisi moved to Rome and was immediately appointed Commander of the Papal Armies by his brother. Setting a precedent for his successor (Pope Urban VIII, who would later make habit commonplace), the Pope also purchased the comune of Fiano from the House of Sforza for 200,000 Écu and Ludovisi was duly appointed Duke of Fiano and also Duke of Zagarolo.