Pope Pius IX was head of the Catholic Church from 1846 to 1878, the longest verified papal reign. He was notable for convoking the First Vatican Council in 1868 and for permanently losing control of the Papal States in 1870 to the Kingdom of Italy. Thereafter he refused to leave Vatican City, declaring himself a "prisoner of the Vatican".
At the time of his election, he was seen as a champion of liberalism and reform, but the Revolutions of 1848 decisively reversed his policies. Upon the assassination of his Prime Minister Rossi, Pius escaped Rome and excommunicated all participants in the short-lived Roman Republic. After its suppression and his return in 1850, his policies and doctrinal pronouncements became increasingly conservative, seeking to stem the revolutionary tide.
In his encyclical Ubi primum he emphasized Mary's role in salvation. In 1854, he promulgated the dogma of the Immaculate Conception, articulating a long-held Catholic belief that Mary, the Mother of God, was conceived without original sin.