As one of the cardinal-nephews of Pope Urban VIII and a supporter of France, he played a significant role at a number of the papal conclaves of the 17th century.

The Pope's forces (12,000 infantry and 3,000 cavalry) were led by Antonio, his brother Taddeo and mercenary field commander Luigi Mattei.

[citation needed] Castro fell to Urban's forces without significant resistance and the victory was celebrated in song by Barberini family composer, Marco Marazzoli.

[2] Pope Urban was forced to accept defeat and signed a peace treaty with the Farnese Dukes in an attempt to prevent them from marching on Rome itself.

[citation needed] Antonio's brother Francesco had sided with the Spanish and split the conclave and it was his negotiations that resulted in Pamphili's election.

[citation needed] For reasons unknown, Pope Innocent X reneged on the deal and Antonio and his brother Taddeo were accused of financial abuses during the War of Castro.

Before leaving Rome, Antonio had the crest of the King of France affixed above his door as a warning to his political rivals that he was now protected by the French Kingdom.

[9] The reconciliation was, in part, engineered by Cardinal Mazarin and Antonio showed his appreciation by holding celebratory services at the San Luigi dei Francesi (Church of St. Louis of the French).

[note 1] Four years later, (1657) the King brought him back to France and transferred him to the Archdiocese of Reims but it took a further decade (1667) before the pope confirmed the post.

[citation needed] Barberini participated in the papal conclave of 1667 during which the French delegation successfully campaigned for the election of Giulio Rospigliosi (Pope Clement IX).

[7] According to the controversial anonymous text The Scarlet Gown (a tabloid published in 1653 listing the vices of each living cardinal of the day), Barberini had a number of mistresses including one he had whipped for flaunting herself during Carnivale and another who died mysteriously while carrying his child.

Contemporary testimony leaves little doubt that the "veritable passion" the cardinal felt extended to more than Pasqualini's beautiful voice.

Marazzoli was appointed Antonio Barberini's aiutante di camera and became a tenor in the papal chapel that same year; in 1639 he was awarded the position of musico under Pope Urban VIII.

Antonio Barberini was appointed prefect of the Congregation and set about commissioning a new palace, the Palazzo del Propaganda Fide.

Antonio and his brothers also commissioned the Teatro delle Quattro Fontane (or Theatre of the Four Fountains); an opera house in Rome and built in 1632.

Antonio had purchased the art collection of Francesco Maria Del Monte upon the cardinal's death which had included a large number of important works.

[17] Today the Palazzo Barberini houses the Galleria Nazionale d'Arte Antica, one of the most important painting collections in Italy.