September Convention

The September Convention was a treaty, signed on 15 September 1864, between the Kingdom of Italy and the French Empire, under which:

Additionally, in a protocol at first kept secret, the Italian government pledged to move its capital from Turin to another city (later selected by a commission to be Florence) within six months, to prove its good faith in giving up all claims on Rome.

This treaty was opposed by the Pope, the French Catholics, and by Italian patriots. When the government’s move to Florence was announced, it caused widespread rioting in Turin, whose repression caused 55 dead and at least 133 wounded among the protesters; however, the King and the Italian government were duly transferred on 3 February 1865 (with the sovereign taking up residence at Palazzo Pitti). The last French troops left Rome in December 1866. Napoleon III hoped that the Italian government and Pope Pius IX would negotiate a compromise that would allow the government to move from Florence to Rome.

Because the intransigent Pius IX rejected all proposals, Italian patriots, under the leadership of Giuseppe Garibaldi, organized an invasion of Latium and Rome in October 1867. The patriots were defeated at Mentana by 2,000 French troops, sent by Napoleon III. A French garrison was kept in Rome to prop up the rule of Pius IX.

In August 1870, following the outbreak of the Franco-Prussian war, the French garrison was recalled from Rome. Widespread public demonstrations demanded that the Italian government take Rome. The Italian government took no direct action until the defeat of Napoleon III at the Battle of Sedan, after which the Italian government was no longer bound by the September Convention. Victor Emmanuel sent Count Gustavo Ponza di San Martino to Pius IX with a personal letter offering a face-saving proposal that would have allowed the peaceful entry of the Italian Army into Rome, under the guise of offering protection to the Pope.

The Italian Army, commanded by General Raffaele Cadorna, crossed the Papal frontier on 11 September and advanced slowly toward Rome, hoping that a peaceful entry could be negotiated. The Italian Army reached the Aurelian Walls on 19 September and placed Rome under a state of siege. Pius IX refused to surrender and the Papal Zouaves kept resisting. On September 20, after a cannonade of three hours had breached the Aurelian Walls at Porta Pia, the Bersaglieri entered Rome and marched down Via Pia, which was subsequently renamed Via XX Settembre. 49 Italian soldiers and 19 Papal Zouaves died. Rome and Latium were annexed to the Kingdom of Italy after a plebiscite. The Pope declared himself a "prisoner in the Vatican". The following year, the Italian government moved from Florence to Rome.

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