Charles V felt threatened by the ever-expanding Turks from the East as well as the Moors pushing up into Spain. Charles also had political problems throughout Europe. Not only was he ruler of Spain, but he also ruled Austria, was named the Holy Roman Emperor (the collection of German states), ruled southern Italy (which would present conflict with the Pope who ruled the Papal States), and Holland ("Black Peter" was the Dutch foil Santa who was dressed in Spanish garb and made to look like the devil).
The preceding Diet of Speier had forbidden the progress of the Reformation. Of course anyone trying to block the spread of the Gospel will not get far. Add to this the Edict of Worms, which declared Martin Luther a heretic and the Lutheran group as outlaws. The Conference at Marburg failed to unite the Lutherans who were divided.
But if there was a "light at the end of the tunnel," it had to be the impending threat from the east. The Turks under Suleiman "the Magnificent," who called himself, "Lord of all rulers, Dispenser of crowns to the monarchs of the earth, the Shadow of God over the world," had reached the summit of their military power, and approached the gates of Vienna in September, 1529. They swore by the beard of Mohammed not to rest till the prayers of the prophet of Mecca should be heard from the tower of St. Stephen. An initial attack left Suleiman with a loss of eighty thousand men. But that didn't stop "the Magnificent One" as he threatened a second attempt, and in the mean time laid waste a great part of Hungary.
Under these clouds the Diet of Augsburg convened on April 8, 1530. The goal was to both settle the religious question and to prepare for war against the Turks. The carefully worded invitation (dated January 21, 1530, from Bologna) was moderating on religious differences but strongly worded on the imminent threat from the Turks.
But there obstacles for such co-operation. The Roman camp sought war against the Protestants as enemies of the church and the Turks as enemies of the state. Luther was worse than Mohammed. Lutherans saw the Papists and the Turks as the enemies of the gospel. The Pope was at least as bad as Mohammed. Their motto was:
