The emperor and his Catholic friends were fearfully alarmed.  Here was a danger more to be dreaded than even the doctrines of Luther.  All the energies of Christendom were requisite to repel this invasion.  The emperor was compelled to appeal to the Protestant princes to cooeperate in this great emergence.  But they had more to fear from the fiery persecution of the papal church than from the cimeter of the infidel, and they refused any cooeperation with the emperor so long as the menaces of the Augsburg decrees were suspended over them.  The emperor wished the Protestants to help him drive out the Turks, that then, relieved from that danger, he might turn all his energies against the Protestants.

After various negotiations it was agreed, as a temporary arrangement, that there should be a truce of the Catholic persecution until another general council should be called, and that until then the Protestants should be allowed freedom of conscience and of worship.  The German States now turned their whole force against the Turks.  The Protestants contributed to the war with energy which amazed the Catholics.  They even trebled the contingents which they had agreed to furnish, and marched to the assault with the greatest intrepidity.  The Turks were driven from Hungary, and then the emperor, in violation of his pledge, recommenced proceeding against the Protestants.  But it was the worst moment the infatuated emperor could have selected.  The Protestants, already armed and marshaled, were not at all disposed to lie down to be trodden upon by their foes.  They renewed their confederacy, drove the emperor’s Austrian troops out of the territories of Wirtemberg, which they had seized, and restored the duchy to the Protestant duke, Ulric.  Civil war had now commenced.  But the Protestants were strong, determined, and had proved their valor in the recent war with the Turks.  The more moderate of the papal party, foreseeing a strife which might be interminable, interposed, and succeeded in effecting a compromise which again secured transient peace.

Charles, however, had not yet abandoned his design to compel the Protestants to return to the papal church.  He was merely temporizing till he could bring such an array of the papal powers against the reformers that they could present no successful resistance.  With this intention he entered into a secret treaty with the powerful King of France, in which Francis agreed to concentrate all the forces of his kingdom to crush the Lutheran doctrines.  He then succeeded in concluding a truce with the Turks for five years.  He was now prepared to act with decision against the reformed religion.