The protestant reformation
In 1512, he returned to Wittenberg to teach and preach. He ignored the Scholasticism of the Middle Ages and concentrated on the Psalms and Epistles of St. Paul. By 1517, there would be no reason to think that Luther was a particularly dissatisfied member of the Church. But 1517 is a very important year. Albert of Hohenzollern was offered the archbishopric of Mainz if he would pay the required fee (Albert already held two bishoprics, even though he had not yet reached the required age to be a bishop!). Pope Leo X asked Albert to pay 12,000 ducats for the twelve apostles but Albert would only offer 7,000 for the seven deadly sins. A compromise was reached and Albert paid 10,000 ducats. Leo proclaimed an indulgence in Albert's territories for eight years with half of the money going to Albert and the other half to construct the basilica of St. Peter's.
The storm broke on October 31, the eve of All Saints Day. On that day Luther nailed a copy of the ninety-five these to the door of the Castle Church at Wittenberg. The Theses (actually 95 statements), all related to the prevalence of indulgences and Luther offered to dispute them all. The day chosen by Luther -- All Saints Day -- was important. All of Wittenberg was crowded with peasants and pilgrims who had come to the city to honor the consecration of the Church. Word of Luther's Theses spread throughout the crowd and spurred on by Luther's friends at the university, many people called for the translation of the Theses into German. A student copied Luther's Latin text and then translated the document and sent it to the university press and from there it spread throughout Germany. It was the printing press itself, that allowed Luther's message to spread so rapidly. [Note: Following the research of Erwin Iserloh, Richard Marius has suggested that perhaps Luther never posted the Ninety-Five Theses. We know, for instance, that Luther wrote a letter to his archbishop complaining about indulgences. The story that Luther nailed the Theses to the church door comes from Philipp Melanchthon (1497-1560), a professor of Greek and one of Luther's colleagues. However, Melanchthon did not arrive in Wittenberg until August of the following year. Luther never mentioned this incident in any of his table talk. See Marius, Martin Luther: The Christian Between God and Death