Late Middle Ages:

Martin Luther, a German monk, started the German Reformation by posting 95 theses on the castle church of Wittenberg on October 31, 1517. The immediate provocation spurring this act was Pope Leo X’s renewal of the indulgence for the building of the new St. Peter's Basilica in 1514. Luther was challenged to recant his heresy at the Diet of Worms in 1521. When he refused, he was placed under the ban of the Empire by Charles V. Receiving the protection of Frederick the Wise, he was then able to translate the Bible into German.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What did Martin Luther post on the castle church of Wittenberg?
95 theses