Capture of Rome The Capture of Rome ( 20 September 1870 ) was the final event of the long process of Italian unification known as the " Risorgimento " , which unified the Italian peninsula under King Victor Emmanuel II of the House of Savoy . Prelude . Second Italian War of Independence . During the Second Italian War of Independence , much of the Papal States had been conquered by the Piedmontese Army , and the new unified Kingdom of Italy was created in March 1861 , when the first Italian Parliament met in Turin . On 27 March 1861 , the Parliament declared Rome the Capital of the Kingdom of Italy . However , the Italian government could not take its seat in Rome because it did not control the territory . In addition , a French garrison was maintained in the city by Napoleon III of France in support of Pope Pius IX , who was determined not to hand over temporal power in the States of the Church . In July 1870 , at the very last moment of the Church ' s rule over Rome , the First Vatican Council was held in the city – affirming the doctrine of papal infallibility . Franco - Prussian War . In July 1870 , the Franco - Prussian War began . In early August , Napoleon III recalled his garrison from Rome . The French not only needed the troops to defend their homeland - Prussian diplomats were actively trying to convince Italy to join the war , so there was real concern that Italy might use the French presence in Rome as a pretext to go to war with France . In the earlier Austro - Prussian War Italy had allied with Prussia and Italian public opinion favoured the Prussian side at the start of the war . The removal of the French garrison eased tensions between Italy and France . Italy remained neutral in the Franco - Prussian War . With the French garrison gone , widespread public demonstrations demanded that the Italian government take Rome . But Rome remained under French protection on paper , therefore an attack would still have been regarded as an act of war against the French Empire . Until events elsewhere took their course the Italians were unwilling to provoke Napoleon , but after the surrender of Napoleon and his army at the Battle of Sedan the situation changed radically . The French Emperor was deposed . The new French government was clearly in no position to retaliate against Italy , nor did it possess the political will to protect the Pope ' s position . Letter to the Pope . King Victor Emmanuel II sent Conte 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 protecting the pope . Along with the letter , the count carried a document that Lanza had prepared , setting out ten articles to serve as the basis for an agreement between Italy and the Holy See . The Pope would retain the inviolability and prerogatives attaching to him as a sovereign . The Leonine city would remain " under the full jurisdiction and sovereignty of the Pontiff " . The Italian state would guarantee the pope ' s freedom to communicate with the Catholic world , as well as diplomatic immunity both for the nuncios and envoys in foreign lands and for the foreign diplomats at the Holy See . The government would supply a permanent annual fund for the pope and the cardinals , equal to the amount currently assigned to them by the budget of the pontifical state , and would assume all papal civil servants and soldiers onto the state payroll , with full pensions as long as they were Italian . According to Raffaele De Cesare : The Pope ’ s reception of San Martino [ 10 September 1870 ] was unfriendly . Pius IX allowed violent outbursts to escape him . Throwing the King ’ s letter upon the table he exclaimed , " Fine loyalty ! You are all a set of vipers , of whited sepulchres , and wanting in faith . " He was perhaps alluding to other letters received from the King . After , growing calmer , he exclaimed : " I am no prophet , nor son of a prophet , but I tell you , you will never enter Rome ! " San Martino was so mortified that he left the next day . Capture . The Italian army , commanded by General Raffaele Cadorna , crossed the papal frontier on 11 September and advanced toward Rome , moving slowly in the hope that a peaceful entry could be negotiated . The Papal garrisons had retreated from Orvieto , Viterbo , Alatri , Frosinone and other strongholds in the Lazio , Pius IX himself being convinced of the inevitability of a surrender . When the Italian Army approached the Aurelian Walls that defended the city , the papal force was commanded by General Hermann Kanzler , and was composed of the Swiss Guards and a few " zouaves " — volunteers from France , Austria , the Netherlands , Spain , and other countries — for a total of 13 , 157 men against some 50 , 000 Italians . The Italian army reached the Aurelian Walls on 19 September and placed Rome under a state of siege . Pius IX decided that the surrender of the city would be granted only after his troops had put up enough resistance to make it plain that the take - over was not freely accepted . On 20 September , after a cannonade of three hours had breached the Aurelian Walls at Porta Pia , the crack Piedmontese infantry corps of Bersaglieri entered Rome . In the event 49 Italian soldiers and 19 Papal Zouaves died . The day ' s events are memorialized throughout Italy in the via XX Settembre in virtually every town of any size . Rome and the region of Lazio were annexed to the Kingdom of Italy after a plebiscite . The Leonine City , including the Vatican , seat of the Pope , was occupied on September 21 . The Italian government had intended to let the Pope keep the Leonine City , but the Pope would not agree to give up his claims to a broader territory . The " Via Pia " , the road departing from Porta Pia , was rechristened " Via XX Settembre " ( September 20 ) . Subsequently , in numerous Italian cities the name " Venti Settembre " was given to the main road leading to the local Cathedral . Writer Edmondo De Amicis took part in the capture of Rome as an officer in the Italian army . Aftermath . For many years afterwards , the Catholic Church remained obdurate in rejecting the results of 1870 . This ended with the Concordat of 1929 , where the Church renounced its claims over most of the city of Rome in return for Italy ' s recognition of the Vatican State . On 20 September 2000 , an item in the Catholic publication " Avvenire " stated : Pius ' s contingency plans . Several times during his pontificate , Pius IX considered leaving Rome . One occurrence was in 1862 , when Giuseppe Garibaldi was in Sicily gathering volunteers for a campaign to take Rome under the slogan " Roma o Morte " ( Rome or Death ) . On 26 July 1862 , before Garibaldi and his volunteers were stopped at Aspromonte : Two other instances occurred after the Capture of Rome and the suspension of the First Vatican Council . These were confided by Otto von Bismarck to Moritz Busch :