When, after the disaster of Sedan, the Parisian population rose and proclaimed the Republic, the Italian Government felt itself absolved from the observance of the agreement made with the French Emperor in 1864; hence the question of intervention in the Papal States could now be debated. Victor Emmanuel wrote a letter to Pius IX in which he implored him, with filial affection, to consider the state of Italy and to renounce the temporal power; but the Pontiff replied that only violence would compel him to do the latter.
On September 19th the Italian troops, under General Raffaele Cadorna, arrived at the gates of Rome; on the 20th, after a short encounter at Porta Pia, they made a breach in the walls. Pius IX, who had wished merely to demonstrate the employment of armed force by the Government, then gave orders to his soldiers to withdraw. Thus was effected one of the most important facts in modern history - the abolition of that temporal power which, originally given by Pepin, had lasted for eleven centuries and had always hindered the unification of Italy.
On the occasion of the opening of the new Parliament in Florence, on December 5, 1870, Victor Emmanuel could with just pride exclaim: "With Rome as the capital of Italy, I have fulfilled my promise and crowned the enterprise that, twenty-three years ago, was initiated under the auspices of my magnanimous father. Both as a monarch and as a son, my heart thrills with a solemn joy as I salute all the representatives of our beloved country, gathered here together for the first time, and pronounce the words: 'Italy is free and united; it only depends on us to make her great and happy.'"
The Italian Parliament, before transferring its sessions to Rome, passed a law - known as the "Law of Guarantees" by which the Pope was insured the enjoyment of all his prerogatives and honors as a sovereign, was awarded the palaces of the Vatican and the Lateran, as well as the villa of Castel Gandolfo - all exempt from any tax or duty - and was assigned an annual income of three million two hundred twenty-five thousand Italian lire. The Pontiff refused to recognize this law or to accept the allowance, and still persisted in maintaining his unavailing protest against the Italian Government.
On July 2, 1871, Victor Emmanuel entered Rome in state, and took up his abode in the palace of the Quirinal, uttering the famous words: "We are at Rome, and here we remain." The Chamber of Deputies monopolized for its sittings the Montecitorio palace, while the Senate took possession of the Madama palace - so called from Margaret of Austria, daughter of Charles V, who formerly lived there.
“Since the fall, God will not trust us with our own salvation, but it is both purchased and kept by Christ for us, and we for it through faith, wrought by the power of God.”
–Richard Sibbes, The Bruised Reed and Smoking Flax