Diet of Worms participant Charles V
Background
In June 1520, Pope Leo X issued the Papal bull Exsurge Domine ("Arise, O Lord"), outlining 41 purported errors found in Martin Luther's Ninety-five Theses and other writings related to or written by him. Luther was summoned by the emperor. Prince Frederick III, Elector of Saxony obtained an agreement that, if Luther appeared, he would be promised safe passage to and from the meeting. This guarantee was essential after the treatment of Jan Hus, who was tried and executed at the Council of Constance in 1415 despite a promise of safe conduct.
Emperor Charles V commenced the Imperial Diet of Worms on 23 January 1521. Luther was summoned to renounce or reaffirm his views. When he appeared before the assembly on 16 April, Johann Eck, an assistant of the Archbishop of Trier, Richard von Greiffenklau zu Vollrads at that time, acted as spokesman for the emperor.