The Diet of Worms officially convened in January 1521. The system of imperial diets was set up by Emperor Maximilian to settle disputes and regulate affairs among imperial states and free cities, though the states and in particular the seven electors had the greatest influence. Luther’s theology was not the reason for the gathering of the diet, though the newly crowned emperor, Charles V, was expected to address the issue. On the eve of Worms, Luther was officially excommunicated through the papal bull Decet Romanem Pontificem and Rome wanted Charles to place the imperial interdict—a civil penalty—on him. Because of the excommunication, Charles revoked Luther’s right to defend himself, but Frederick the Wise attempted to persuade the emperor otherwise. His efforts resulted in the March summons for Luther to appear in April.
In the period between January and April, the Roman and German sides were at odds preparing for Luther’s hearing. The German imperial states, led by Frederick the Wise, sought a fair trial for Luther before an impartial body of judges. Their motivation was the reform of the church. The imperial states had repeatedly delivered a list of grievances against Rome, or Gravamina, at imperial diets and many of their concerns regarding Roman interference in German churches were reflected in Luther’s Address to the Christian Nobility. Rome, on the other hand, did not believe ecclesiastical decisions should be left to an imperial council and instead wanted the emperor to place the interdict on Luther if he were unwilling to recant. Charles sided with the Germans and Frederick secured from him a promise of safe conduct. When Luther received the summons, he believed a fair trial and an open debate awaited him in Worms.
Luther arrived in April to a different setting than he had expected. When he finally stood before the imperial council on April 17, a stack of his books was laid out on a table and a representative of the archbishop of Trier asked him whether the books were his and, if so, whether he would recant of their teachings. Luther himself was flustered at the absence of the debate he anticipated and after a mumbled response asked for more time to consider his answer. After a long day of imperial business, Luther appeared again before the council the following evening. In response to his interrogator, he affirmed his authorship of all the books and placed his writings in three categories. The first group dealt with piety and morals and he deemed them generally uncontested, even by the papal bull excommunicating him. The second group was directed at the errors of the papacy which he believed threatened the faithful and so he refused to recant of them. The third set of writings included those Luther had directed against supporters of the papacy who defended the errors he criticized in the second category, and he likewise would not retract those. His interrogator was not satisfied with the response and demanded Luther provide a direct answer “without horns” to the question of whether he recanted of the arguments in his books. Luther then uttered his famous reply that unless he were convinced by Scripture or clear reason, he was bound to the Word of God and his conscience captive to it.
The fallout from Luther’s stand was immediate. He expected death, while Rome pressed for the same. On April 26, he and his traveling companions left on their return journey to Wittenberg. However, Frederick the Wise had arranged discreetly to stage a surprise attack on the party, where armed soldiers would seize Luther and relocate him to an unspecified location for his own protection. The destination was the Wartburg Castle, where he would stay for the next ten months until problems in Wittenberg demanded his return. During his seclusion, Charles V published the Edict of Worms, which supported the bull of excommunication and declared Luther an outlaw.