From Textus Receptus
The Protestant Reformation was the 16th-century schism within Western Christianity initiated by Martin Luther, John Calvin and other early Protestants. It was sparked by the 1517 posting of Luther's Ninety-Five Theses. The efforts of the self-described "reformers", who objected to ("protested") the doctrines, rituals, and ecclesiastical structure of the Roman Catholic Church, led to the creation of new national Protestant churches. The Reformation was precipitated by earlier events within Europe, such as the Black Death and the Western Schism, which eroded people's faith in the Catholic Church and the Papacy which governed it. This, as well as many other factors, such as the mid 15th-century invention of the printing press, and the fall of the Eastern Roman Empire, contributed to the creation of Protestantism.
The Roman Catholic Church responded with a Counter-Reformation put in to motion by the Council of Trent—the most important ecumenical council since Nicaea II 800 years earlier (at the time, there had not been an ecumenical council since Lateran IV over 300 years prior, a length only to be matched by the interval between Trent and Vatican I )—and spearheaded by the Society of Jesus. In general, Northern Europe, with the exception of Ireland and pockets of Britain and the Netherlands, turned Protestant. Southern Europe remained Roman Catholic, while fierce battles which turned into warfare took place in central Europe.
The largest of the new churches were the Lutherans (mostly in Germany, the Baltics and Scandinavia) and the Reformed churches (mostly in Germany, Switzerland, the Netherlands and Scotland). There were many smaller bodies as well. The most common dating of the Protestant Reformation begins in 1517, when Luther published The Ninety-Five Theses, and concludes in 1648 with the Treaty of Westphalia that ended years of European religious wars.