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. With the French garrison gone, widespread public demonstrations demanded that the Italian government take Rome.
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".
Although Prussian prime minister Otto von Bismarck was no friend of the papacy, he knew any war that put Prussia and the Holy See in opposing alliances would almost certainly have upset the delicate pan-German coalition, and with it his own carefully laid-out plans for national unification.
For both Prussia and Italy, any misstep that caused the breakup of the pan-German coalition brought with it the risk of Austro-Hungarian intervention in a wider European conflict.
Above all else, Bismarck made every diplomatic effort to keep Prussia's conflicts of the 1860s and 1870s localized and prevent them from spiraling out of control into a general European war.
With that development, the prospect of a conflict on the Italian peninsula provoking foreign intervention all but vanished.
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.
On the following day, the pope himself was besieged by a large crowd of outraged protesters assembling at the Quirinal Palace.
Palma, a papal prelate, who was standing at a window, was shot, and Pius IX then decided to flee Rome and concede his temporal rule to an Italian constitutional republic.