Although there had been earlier attempts to reform the Catholic Church – such as those of Jan Hus, Peter Waldo, John Wycliffe, and Girolamo Savonarola – Luther is widely acknowledged to have started the Reformation with the Ninety-five Theses. Luther began by criticising the sale of indulgences, insisting that the Pope had no authority over purgatory and that the Catholic doctrine of the merits of the saints had no foundation in the Bible. The Reformation incorporated doctrinal changes such as a complete reliance on Scripture as the only source of proper belief (sola scriptura) and the belief that faith in Jesus, and not good works, is the only way to obtain God's pardon for sin (sola fide). The core motivation behind these changes was theological, though many other factors played a part, including the rise of nationalism, the Western Schism that eroded loyalty to the Papacy, the perceived corruption of the Roman Curia, the impact of humanism, and the new learning of the Renaissance that questioned much traditional thought.
The initial movement in Germany diversified, and other reformers arose independently of Luther. The groundwork of the Reformation was developed by three major reformers: Luther in Wittenberg, Zwingli in Zürich and Calvin in Geneva. Depending on country, the Reformation had varying causes, background, and also unfolded differently than in Germany. The spread of Gutenberg's printing press provided the means for the rapid dissemination of religious materials in the vernacular. Lutheran churches were founded in Germany, the Baltics and Scandinavia, and Reformed ones in Switzerland, Hungary, France, the Netherlands and Scotland. The movement influenced the Church of England after 1547, under Edward VI and Elizabeth I, although the English Reformation had begun under Henry VIII in 1534.
Reformation movements throughout continental Europe known as the Radical Reformation gave rise to various Anabaptist movements. Radical Reformers, besides forming communities outside state sanction, often employed more extreme doctrinal change, such as the rejection of the tenets of the councils of Nicaea and Chalcedon. Anabaptism suffered a major blow early in the German Peasants' War and was persecuted for centuries since that.
The Catholic Church responded with a Counter-Reformation, initiated by the Council of Trent in 1545, and a new order, the Jesuits, founded in 1540. Northern Europe, with the exception of most of Ireland, came under the influence of Protestantism. Southern Europe remained Catholic. Central Europe became a site of a fierce conflict that culminated in the Thirty Years' War.
The oldest Protestant churches, such as the Unitas Fratrum and Moravian Church, date their origins to Jan Hus (John Huss) in the early 15th century. As it was led by a Bohemian noble majority, and recognised, for a time, by the Basel Compacts, the Hussite Reformation was Europe's first "Magisterial Reformation" because the ruling magistrates supported it, unlike the "Radical Reformation", which the state did not support.