The Lateran Treaty Made the Pope a Head of State

In September 1870, Italian nationalist forces entered Rome through a breach in the Aurelian Wall, completing the unification of Italy and ending the Papal States. Pope Pius IX retreated behind the walls of the Vatican and declared himself a prisoner. For the next 59 years, every subsequent pope refused to leave Vatican grounds or acknowledge the Italian state.

The impasse ended on February 11, 1929, when Cardinal Secretary of State Pietro Gasparri and Benito Mussolini's Prime Minister signed three documents in the Lateran Palace: a political treaty, a concordat, and a financial agreement.

The political treaty created Vatican City as an independent sovereign state of 44 hectares — the smallest internationally recognized country in the world by both area and population. Italy recognized the Holy See's sovereignty; the Holy See recognized Italy's sovereignty over Rome. The concordat recognized Catholicism as Italy's state religion and gave church marriages full legal standing. The financial convention provided 750 million Italian lire and one billion lire in Italian state bonds as compensation for the loss of the Papal States.

Mussolini's motivations were strategic. He had suppressed Catholic lay organizations and was in direct competition with the Church for Italian civil society. A diplomatic settlement that formalized the Vatican's international legal status also removed the Church as a domestic political rival — at least temporarily. Pope Pius XI called the settlement a "good thing surrounded by much that is not good." The concordat was revised in 1984, when Italy formally disestablished Catholicism as the state religion.