Pius IX, 1792–1878, pope (1846–78), an Italian named Giovanni M. Mastai-Ferretti, b. Senigallia; successor of Gregory XVI. He was cardinal and bishop of Imola when elected pope. For two years he pursued a progressive policy in governing the Papal States and granted a constitution. However, in 1848 rioting drove him from Rome to Gaeta, and he returned (1850) to be supported in power only by the forces of Napoleon III. The Italian nationalists were eager for Rome and the Papal States, and in 1860 Victor Emmanuel II seized all but Rome and its neighborhood. In 1870, on the deposition of Napoleon III, the Italians entered Rome, and Pius retired to the Vatican, refusing to recognize the new kingdom and to accept the proffered indemnity. The anomalous situation, called the Roman Question, was settled eventually by the Lateran Treaty. Pius's dealings with other nations were unfortunate, and he did not conduct his side of the Kulturkampf with the finesse of his successor. In 1854, Pius declared the dogma of the Immaculate Conception of the Virgin to be an article of faith. In 1864 he issued the encyclical Quanta cura, accompanied by a list ( Syllabus ) of erroneous modernistic statements. In 1869 he convoked the First Vatican Council, the principal work of which was the enunciation of papal infallibility. Pius IX's pontificate—the longest in history—helped define the role of Roman Catholicism in the modern world. He was succeeded by Leo XIII. Pius IX was beatified in 2000 by John Paul II.