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Why did Pope Pius IX call himself a prisoner of the Vatican?

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Photograph of Pope Pius IX — Pius IX Pius IX is the longest-reigning pope in the history of the Roman Catholic Church. His pontificate lasted from 1846 to 1878.

Pope Pius IX declared himself a "prisoner of the Vatican" following the capture of Rome by Italian troops on September 20, 1870. This event marked the final stage of the Risorgimento, the movement for Italian unification, and resulted in the end of the Papal States as a temporal power.1234

Pius IX adamantly refused to recognize the legitimacy of the new Italian state or the loss of his temporal authority, which he believed was essential to protect his spiritual independence. By withdrawing into the Vatican palace and refusing any formal intercourse with the Italian government, he signaled his protest against the occupation. He also rejected the Law of Guarantees, an 1871 legislative attempt by the Italian government to regulate the status of the papacy and provide financial compensation for the loss of papal territories. This standoff, known as the Roman question, persisted until the Lateran Treaty of 1929, which finally established Vatican City as an independent state.51234