The capture of Rome on 20 September 1870 was a significant moment in European history, marking the end of papal temporal power and the completion of Italy’s unification. This event, a conclusion of the nationalist Risorgimento movement, permanently changed Italy's political landscape and redefined the relationship between the state and the Catholic Church. It signaled the Papal States’ annexation into the Kingdom of Italy and the establishment of Rome as its capital.
The Papal States, which had existed since the 8th century, were the last remaining barrier to Italy’s national alliance. Pope Pius IX, however, was determined to maintain his sovereignty over the region despite the growing momentum of Italian unification under King Victor Emmanuel II. As Italian forces closed in on Rome, the pope’s diplomatic options dwindled, setting the stage for a military confrontation.
On 18 September 1870, Italian Minister of War Cesare Ricotti-Magnani ordered General Raffaele Cadoma to initiate the attack on Rome, with instructions to spare the Leonine City, which housed the Vatican. The Italian soldiers laid siege to the city’s ancient Aurelian Walls the following day, facing a vastly outnumbered Papal force composed of Swiss Guards, Papal Zouaves and volunteers from various European nations. While the defenders numbered just over 13,000, the Italian military had more than 50,000 soldiers.
At dawn on 20 September, Italian artillery opened fire on the city’s fortifications. By late morning, the Italian forces had broken the walls near Porta Pia and the battle was over. The fighting was not prolonged but left casualties on both sides, with 49 Italian and 19 Papal soldiers killed. By early afternoon, the terms of surrender were signed and Rome was annexed into the Kingdom of Italy, though the Vatican and its surrounding territory were left safe.
The Italian government held a referendum on 2 October 1870 to legitimate the capture of Rome, which overwhelmingly endorsed unification.
However, Pope Pius IX refused to recognise the annexation, issuing an encyclical condemning the Italian forces and excommunicating those involved. He announced himself a “Prisoner in the Vatican,” commencing a decades-long stand-off.
Rome's capture marked the final chapter of the Risorgimento and the fall of the Papal States. Rome became the capital of a unified Italy, while the pope’s role was confined to spiritual leadership within the Vatican. This pivotal event reformed Italy’s national identity and signalled the close of papal rule over secular affairs, transforming the balance of power between church and state in modern Italy.
