What does PIUS stand for? 

Pius

the name of nine Popes, of which only six call for particular mention: P. II., Pope from 1458 to 1464, was of the family of the Piccolomini, and is known to history as Æneas Sylvius, and under which name he did diplomatic work in Britain and Germany; as Pope he succeeded Callistus III.; he was a wily potentate, and is distinguished for organising a crusade against the Turks as well as his scholarship; the works which survive him are of a historical character, and his letters are of great value. P. IV., from 1559 to 1563, was of humble birth; during his popehood the deliberations of the Council of Trent were brought to a close, and the Tridentine Creed was named after him. P. V., Pope 1566 to 1572, also of humble birth, was severe in his civil and ecclesiastical capacity, both in his internal administration and foreign relationships, and thought to browbeat the world back into the bosom of Mother Church; issued a bull releasing Queen Elizabeth's subjects from their allegiance; but the great event of his reign, and to which he contributed, was the naval victory over the Turks at Lepanto in 1571. P. VI., Pope from 1775 to 1799; the commencement of his popehood was signalised by beneficent measures for the benefit of the Roman city, but he was soon in trouble in consequence of encroachments on Church privileges in Austria and the confiscation of all Church property in France, which ended, on his resisting, to still further outrages, in his capture by the French under Bonaparte and his expatriation from Rome. P. VII., Pope from 1800 to 1823, concluded a concordat with France, crowned Napoleon emperor at Paris, who thereafter annexed the papal territories to the French empire, which were in part restored to him only after Napoleon's fall; he was a meek-spirited man, and was much tossed about in his day. P. IX., or Pio Nono, from 1846 to 1878, was a "reforming" Pope, and by his concessions awoke in 1848 a spirit of revolution, under the force of which he was compelled to flee from Rome, to return again under the protection of French bayonets against his own subjects, to devote himself to purely ecclesiastical affairs; in 1854 he promulgated the doctrine of the Immaculate Conception, and in 1869 the Infallibility of the Pope; upon the outbreak of the Franco-German War in 1871 the French troops were withdrawn and Victor Emmanuel's troops entered the city; Pius retired into the Vatican, where he lived in seclusion till his death.

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