Luther became increasingly angry about the clergy selling 'indulgences' - promised remission from punishments for sin, either for someone still living or for one who had died and was believed to be in purgatory. On 31 October 1517, he published his '95 Theses', attacking papal abuses and the sale of indulgences.
Luther had come to believe that Christians are saved through faith and not through their own efforts. This turned him against many of the major teachings of the Catholic Church. In 1519 -1520, he wrote a series of pamphlets developing his ideas - 'On Christian Liberty', 'On the Freedom of a Christian Man', 'To the Christian Nobility' and 'On the Babylonian Captivity of the Church'. Thanks to the printing press, Luther's '95 Theses' and his other writings spread quickly through Europe.
In January 1521, the Pope Leo X excommunicated Luther. He was then summoned to appear at the Diet of Worms, an assembly of the Holy Roman Empire. He refused to recant and Emperor Charles V declared him an outlaw and a heretic. Luther went into hiding at Wartburg Castle. In 1522, he returned to Wittenberg and in 1525 married Katharina von Bora, a former nun, with whom he had six children.
Luther then became involved in the controversy surrounding the Peasants War (1524 - 1526), the leaders of which had used Luther's arguments to justify their revolt. He rejected their demands and upheld the right of the authorities to suppress the revolt, which lost him many supporters.
In 1534, Luther published a