He began to see now that the whole system of Romish government was wrong, and that there were countless abuses to be swept away before the Church could truly claim to point the way to Christianity. Conscience or authority, the Scriptures or the Church, Germany or Rome? A choice had to be made, each man ranging himself on one side or the other. The independence of Germany was dear to Luther's heart. He wrote an address to the nobles and summoned the Christian princes of Germany to his aid. He declared that all Christians were priests, and that the Church and nation ought to be freed from the interference of the Papacy. He was becoming an avowed enemy of the Pope, losing his former reluctance to attack authority. A Bull was, of course, issued against him, but the students of Erfurt threw the paper on which it was written into the river, saying contemptuously--"It is a bubble, let it swim!" In December, 1520, Luther himself burnt the Bull on a fire kindled for the purpose at the Elster Gate of Wittenberg. He said, as he committed the document to the flames, "As thou hast vexed the saints of God, so mayest thou be consumed in eternal fire." The act cut him off from the Papacy for ever. He had defied the Pope in the presence of many witnesses. {57} Charles V, the Holy Roman Emperor, was not in a position to take up the cause of Luther against his powerful enemies. He maintained an alliance with the Pope so that he would oppose the vast schemes which his rival, Francis I of France, was maturing. At the same time, he owed a debt of gratitude to the Elector Frederick, who was one of the seven German princes possessing the right to "elect" a new emperor. He decided, after a brief struggle, to yield to the demands of the Papal Legates. He ordered Martin Luther to come to Worms and appear before the great Diet, or Assembly of German rulers, which met in 1521. Luther obeyed at once, making a triumphant journey through many towns and villages. Music fell on his ears pleasantly, a portrait of Savonarola was sent to him that he might feel his courage strengthened. Had not his resolve been fixed, he would have turned back at Weimar, where he found an edict posted on the walls ordering all his writings to be burnt. "I am lawfully called to appear in that city," he said, "and thither will I go in the name of the Lord, though as many devils as there are tiles on the houses were there combined against me." He was stricken with illness at Eisenach, but went on as soon as he recovered. When he caught sight of the old towers of Worms, his spirit leapt with joy, and he began to sing his famous hymn, "_Ein feste Burg ist unser Gott._" ("A mighty fortress is our God.")