Rome then became the focus of hopes of Italian reunification after the rest of Italy was united as the Kingdom of Italy in 1861 with the temporary capital in Florence. That year Rome was declared the capital of Italy even though it was still under the Pope's control. During the 1860s, the last vestiges of the Papal States were under French protection thanks to the foreign policy of Napoleon III. French troops were stationed in the region under Papal control. in 1870 the French troops were withdrawn due to the outbreak of the Franco-Prussian War. Italian troops were able to capture Rome entering the city through a breach near Porta Pia. Pope Pius IX declared himself a prisoner in the Vatican. In 1871 the capital of Italy was moved from Florence to Rome. In 1870 the population of the city was 212,000, all of whom lived with the area circumscribed by the ancient city, and in 1920, the population was 660,000. A significant portion lived outside the walls in the north and across the Tiber in the Vatican area.