Why did Pope Pius IX oppose Italian unification?

Pope Pius IX opposed Italian unification primarily because he believed that the preservation of his spiritual authority was inextricably linked to his continued exercise of temporal power as a ruler of the Papal States.1

While Pius IX initially showed interest in liberal reforms upon his accession in 1846, he became convinced that the movements for liberalism and nationalism were inherently revolutionary and posed a direct threat to the church. He concluded that political concessions to these movements led to attacks on his spiritual power, and he viewed the Risorgimento—the movement for Italian unification—as an aggressive force that sought to dismantle the papacy's independence.12

Ultimately, Pius IX refused to recognize the legitimacy of the new Italian kingdom, which he viewed as an obstacle to the church's mission. Following the occupation of Rome by Italian troops in 1870, he declared himself a "prisoner in the Vatican," a stance of non-recognition that persisted until the Lateran Treaty of 1929.13