In 1520, Pope Leo X issued the Papal Bull Exsurge Domine –translates as Arise, O Lord –detailing forty-one errors he claimed to have found in Martin Luther's Ninety-five Theses and others of his writing, thus Luther was summoned by the Holy Roman Emperor, Charles V of Spain to account for himself at the Diet of Worms.
Prince Frederick III, Elector of Saxony negotiated an agreement that if Luther appeared at the assembly he would be promised safe passage to and from the assembly.
Despite the guarantee Luther faced a serious risk in being there. Jan Huss had done the same at the Council of Constance in 1415, following which he was arrested and executed.
The recently elected the emperor commenced the Imperial Diet of Worms on 28 January 1521. Luther was called on 16 April to renounce his views, Johann Eck, an assistant of the Archbishop of Trier acted as spokesman for the emperor. After deliberation Luther returned and said that he was bound by the scriptures and would not recant his writings but would apologise for some of the abrasive tones in which he had written them.
The assembly then adjourned to consider a sentence against him, Afraid of what had happened to John Huss at Constance Luther fled into the protection of Frederick III, Elector of Saxony at Wartburg Castle where he began his translation of the bible into German. Shortly after Luther’s hasty departure the Edict of Worms was issued on 25 May 1521