of Saxony and his allies. In the negotiations at Passau in the summer of 1552, even the Catholic princes had called for a lasting peace, fearing the religious controversy would never be settled. The emperor, however, was unwilling to recognize the religious division in Western Christendom as permanent. This document was foreshadowed by the Peace of Passau, which in 1552 gave Lutherans religious freedom after a victory by Protestant armies. Under the Passau document, Charles granted a peace only until the next imperial Diet, whose meeting was called in early 1555. The treaty, negotiated on Charles' behalf by his brother, Ferdinand, effectively gave Lutheranism official status within the domains of the Holy Roman Empire, according to the policy of cuius regio, eius religio. Knights and towns who had practiced Lutheranism for some time were exempted under the Declaratio Ferdinandei, but the Ecclesiastical reservation supposedly prevented the principle of cuius regio, eius religio from being applied if an ecclesiastical ruler converted to Lutheranism. Main principles The Peace of Augsburg contained three main principles: The principle of ("Whose realm, his religion") provided for internal religious unity within a state: the religion of the prince became the religion of the state and all its inhabitants. Those inhabitants who could not conform to the prince's religion were allowed to leave: an innovative idea in the 16th century. This principle was discussed at length by the various delegates, who finally reached agreement on the specifics of its wording after examining the problem and the proposed solution from every possible angle. The second principle, called the (ecclesiastical reservation), covered the special status of the ecclesiastical state. If the prelate of an ecclesiastic state changed his religion, the inhabitants of that state did not have to do so. Instead, the prelate was expected to resign from his post, although this was not spelled out in the agreement. The third principle, known as (Ferdinand's Declaration), exempted knights and some of the cities from the requirement of religious uniformity, if the reformed religion had been practiced there since the mid-1520s. This allowed for a few mixed cities and towns where Catholics and Lutherans had lived together. It also protected the authority of the princely families, the knights and some of the cities to determine what religious uniformity meant in their territories. Ferdinand inserted this at the last minute, on his own authority. The third principle exempted knights and some