The Protestant princes refused to submit on the ground that their doctrines were in harmony with the Word of God, and to justify this contention Melanchthon published the /Apologia Confessionis Augustanae/, which was in many points more full and explicit than the Confession itself. Some of the German cities that had embraced the Zwinglian doctrine, notably, Strassburg and Constance, repudiated the Augsburg Confession, and presented a document embodying their beliefs, known as the /Confessio Tetrapolitana/ which found no favour with Charles V. or with the Diet. Finally, on the 18th November, the Emperor announced to the Diet that until a General Council should meet, everything must be restored to the /status quo/, that he felt it incumbent upon him as protector of the Church to defend the Catholic faith with all his might, and that in this work he could count on the full support of the Catholic princes. Unfortunately, it was by no means correct to state that the Catholic rulers of Germany stood behind their Emperor. Nearly all of them were anxious to avoid civil war at any cost, and not a few of them hesitated to support the Emperor lest the suppression of the Protestant princes might lead to the establishment of a strong central power. Nor were the Protestants alarmed by the threat of force. With the Turks hovering on the flanks of the empire, they were confident that they might expect concessions rather than violence. The Protestant princes met in December (1530) at Schmalkald to consider their position, and early in the following year (1531) they formed the Schmalkaldic League for the defence of their religious and temporal interests. Negotiations were opened up with France, Denmark, and England, and notification was made to the Emperor that they must withhold their assistance against the Turks until their religious beliefs were secured. They refused, furthermore, to recognise Ferdinand, brother of Charles V., whom Charles had proclaimed King of the Romans. The Emperor, alarmed by the news that Soliman was preparing an immense army for a general attack on Italy and Austria, and well aware that he could not count either on the assistance of the Catholic princes or the neutrality of France, was forced to give way. In July 1532 peace was concluded at Nurnberg. According to the terms of the Peace of Nurnberg it was agreed that until a General Council should assemble no action should be taken against the Protestant princes, and that in the interval everything was to remain unchanged. This agreement, it was stipulated, should apply only to those who accepted the Confession of Augsburg, a stipulation that was meant to exclude the followers of Zwingli.