The September Convention was a treaty concluded in September 1864 between the Papal States and the new Kingdom of Italy, which had recently been founded after the Kingdom of Sardinia annexed most of the small states in the Italian peninsula and most of the territory of the Papal States. The remaining territory of the Papal States was only the city of Rome and some surrounding countryside along the west coast of Italy. King Victor Emanuel II of Italy promised not to invade and annex what was left of the Papal States. Pope Pius IX in return promised to remove French troops from Rome within three years. Not long after the French army left, they were brought back because of a perceived military threat. On September 20, 1870, the Italian army conquered Rome and the pope declared himself a "prisoner in the Vatican". The following year, the capital of Italy was moved from Florence to Rome and the Pope's residence, the Quirinal Palace, was confiscated and became the King's residence. Today it is the Italian President's residence.