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How did the annexation of Rome affect Pope Pius IX’s temporal power?

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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.

The annexation of Rome by Italian troops on September 20, 1870, marked the final end of the Papal States and the total loss of Pius IX’s temporal power.12

Pius IX viewed his temporal authority as essential for protecting his spiritual power, believing the two were indissolubly linked. Consequently, he adamantly refused to recognize the new political reality or the legitimacy of the Italian state. Following the annexation, he withdrew into the Vatican, regarding himself as a "prisoner" and refusing all formal intercourse with the Italian government.213

Although the Italian government attempted to settle the matter through the Law of Guarantees in 1871—which offered the pope a substantial income, sovereign status, and control over the Vatican and Lateran palaces—Pius IX rejected the legislation. This impasse, known as the Roman question, remained unresolved until the Lateran Treaty of 1929 established the independent state of Vatican City.321