Delayed by the war with France and Turkey, the diet for the settlement of the religious difficulty did not meet at Augsburg until February 1555. Ferdinand represented his brother, and after a prolonged discussion conditions of peace were arranged. Romanists and Lutherans were placed upon an equal footing, but the toleration which was granted to them was not extended to the Calvinists. Each secular prince had the right to eject from his land all those who would not accept the form of religion established therein; thus the principle of _cujus regio ejus religio_ was set up. Although the Lutherans did not gain all their demands, they won solid advantages and were allowed to keep all ecclesiastical property secularized before the peace of Passau. A source of trouble, however, was the clause in the treaty usually called the ecclesiastical reservation. This required an ecclesiastical prince, if he accepted the teaching of the confession of Augsburg, or in other words became a Lutheran, forthwith to resign his principality. The Lutherans denied the validity of this clause, and notwithstanding the protests of the Roman Catholics several prelates became Lutheran and kept their territories as secular possessions. The peace of Augsburg can hardly be described as a satisfactory settlement. Individual toleration was not allowed, or only allowed in unison with exile, and in the treaty there was abundant material for future discord.
After Maurice of Saxony had made terms with Charles at Passau he went to help Ferdinand against the Turks, but one of his allies, Henry II. of France, continued the war in Germany while another, Albert Alcibiades, entered upon a wild campaign of plunder in Franconia. The French king seized Metz, which was part of the spoil promised to him by his allies, and Charles made an attempt to regain the city. For this purpose he took Albert Alcibiades into his service, but after a stubborn fight his troops were compelled to retreat in January 1553. Albert then renewed his raids, and these became so terrible that a league of princes, under Maurice of Saxony, was formed to crush him; although Maurice lost his life at Sievershausen in July 1553, this purpose was accomplished, and Albert was driven from Germany. After the peace of Augsburg, which was published in September 1555, the emperor carried out his intention of abdicating. He entrusted Spain and the Netherlands to Philip, while Ferdinand took over the conduct of affairs in Germany; although it was not until 1558 that he was formally installed as his brother's successor.