The Protestant Reformation began in 1517 when Martin Luther publicly protested corrupt practices in the Catholic Church by nailing his 95 Theses to a church door in Germany. This sparked divisions in the Catholic Church and the emergence of Protestantism. Key figures like Luther and John Calvin rejected the authority of the Pope and certain Catholic doctrines, believing salvation came from faith alone rather than good works. The Reformation led to the permanent split of Western Christianity into Catholic and Protestant denominations and spread Protestant ideas across Europe through the 16th century, resulting in religious conflicts and wars.