The pope formed the celebrated Holy League to arrest the progress of the new opinions; and this led all the princes of the empire, who had espoused the Lutheran doctrines, more openly and cordially to combine in self-defense.

In every country in Europe the doctrines of the reformer spread rapidly, and the papal throne was shaken to its base.
Charles V., whose arms were successful in southern Europe, and whose power was daily increasing, was still very desirous of restoring quiet to Europe by reestablishing the supremacy of the papal Church, and crushing out dissent.

He accordingly convened another diet at Spires, the capital of Rhenish Bavaria, on the 15th of March, 1529.

As the emperor was detained in Italy, his brother Ferdinand presided.

The diet was of course divided, but the majority passed very stringent resolutions against the Reformation.