The Protestant Reformation, often simply called The Reformation, was one of several schisms, or splits in church doctrine, in the medieval church. Beginning early in the 16th century, the Reformation arose as a movement by reformers seeking to end abuses of church doctrine by officials within the church, including the Pope himself, and eventually led to the splintering off of several new "protestant" churches with amended doctrines in protest of the catholic church.
A German monk named Martin Luther is often credited with setting off the Reformation with his 95 Theses, which he nailed to the door of the church in Wittenberg on 31 October, 1517, outlining many pointed questions he had regarding certain practices he had observed in the church. Chief among these was the buying and selling of indulgences, though he also had several questions about the use of funds derived from church offerings as well as those derived from the sale of indulgences. Perhaps most disturbing to Pope Leo X, however, were Luther's questions regarding the granting of absolution, which Luther saw as a gift freely offered from God, which no man could claim to sell. This seemed to place limitations on the Pope's authority to grant absolution and reject papal infallibility, as the Pope was in fact signing letters of indulgence in order to raise funds for the church coffers. The resulting dispute culminated in the Diet of Worms in 1521, the outcome of which left Luther both excommunicated from the church and outlawed by temporal authorities.
While Martin Luther spent time translating the Bible into German, and later returned to the church in Wittenberg to suppress, through his sermons, radicalism there, more radical reformers in other parts of the Empire fomented unrest, leading to the German Peasants War in 1524-25. Throughout the 1520s, Luther continued to actively reform the church in Saxony, incorporating more German-language matter into the services, in order to make the mass more accessible to "the simple man". His German-language hymns and his German translations of the Bible are widely credited with quickly spreading the Lutheran Church doctrine throughout the Empire.