Born Enea Silvio Piccolomini at Corsignano in 1405, he studied at the universities of Siena and Florence. His Commentaries is the only autobiography ever written by a reigning Pope. After serving as secretaries to several bishops, in 1447 he was appointed Bishop of Trieste. In 1450 he became Bishop of Siena. He was named a cardinal in 1456, and was elected Pope two years later. In the 1460 papal Bull “Execrabilis”, he condemned all appeals from the decisions of the pope to an oecumenical council, an issue that had been brewing for over a century. This is credited with putting an end to the conciliarist movement. In the early period of his life he was, like many humanists, frivolous and immoral in conduct and writing. More earnest were his conceptions and manner of life after his entrance into the ecclesiastical state. As pope he was indeed not sufficiently free from nepotism, but otherwise served the best interests of the Church. He instituted a commission for the reform of the Roman court and seriously endeavoured to restore monastic discipline.
(Adapted from the 1911 Catholic Encyclopedia)