Lateran Treaty
Negotiations for the settlement of the Roman Question began in 1926 between the government of Italy and the Holy See, and culminated in the agreements of the Lateran Pacts, signed—the Treaty says—for King Victor Emmanuel III of Italy by Benito Mussolini, Prime Minister and Head of Government, and for Pope Pius XI by Pietro Gasparri, Cardinal Secretary of State, on 11 February 1929. It was ratified on 7 June 1929. The agreements were signed in the Lateran Palace, hence the name by which they are known.
Christianity in Italy
The defeat of the Pope by the Kingdom of Italy gave rise to a long period of antagonism between ecclesiastical and Italian powers. This resulted in the Catholic Church suggesting its believers not to take part in the affairs of the Kingdom of Italy, and the consequent laicisation of Italian politics. The Kingdom of Italy and the Catholic Church managed to reapproach under Fascism with the stipulation of the Lateran Treaty. Among other things, the treaty allowed for the foundation of Vatican City, a microstate over which the Pope has full jurisdiction. The Lateran Treaty survived the fall of Fascism and the constitution of the Republic of Italy, and remains valid to these days.