Thus ended the first stage of the Thirty Years' War, although some desultory fighting continued between the League and its opponents. The second began in 1625 with the formation, after much fruitless negotiation, of a Protestant combination, which had the support of England, although its leading member was Christian IV., king of Denmark, who as duke of Holstein was a prince of the Empire, and who like other Lutherans was alarmed at the emperor's successes. It was in this war that Europe first became familiar with the great name of Wallenstein. Unable himself to raise and equip a strong army, and restive at his dependence on the League, Ferdinand gladly accepted Wallenstein's offer to put an army into the field at no cost to himself. After Wallenstein had beaten Mansfeld at the bridge of Dessau in April 1626, and Tilly had defeated Christian of Denmark at Lutter in the succeeding August, the two generals united their forces. Denmark was invaded, and Wallenstein, now duke of Friedland, was authorized to govern the conquered duchies of Mecklenburg and Pomerania; but his ambitious scheme of securing the whole of the south coast of the Baltic was thwarted by the resistance of the city of Stralsund, which for five months he vainly tried to take. Denmark, however, was compelled to conclude peace at Lübeck in May 1629. Dismissal of Wallenstein. Intoxicated by success, Ferdinand had issued two months before the famous Edict of Restitution. This ordered the restoration of all ecclesiastical lands which had come into the possession of the Protestants since the peace of Passau in 1552, and, as several archbishoprics and bishoprics had become Protestant, it struck a tremendous blow at the emperor's foes and stirred among them intense and universal opposition. A little later, yielding to Maximilian and his colleagues in the League, Ferdinand dismissed Wallenstein, whose movements had aroused their resentment, from his service. A more inauspicious moment could not have been chosen for these two serious steps, because in the summer of 1630 Gustavus Adolphus left Sweden at the head of a strong army for the purpose of sustaining the Protestant cause in Germany. At first this great king was coldly received by the Protestants, who were ignorant of his designs and did not want a stranger to profit by the internal disputes of their country. A mistake at the outset would probably have been fatal to him, but he saw the dangers of his position and moved so warily that in less than a year he had obtained the alliance of the elector of Saxony, a consequence of the terrible sack of Magdeburg by the imperialists in May 1631 and of the devastation of the electorate by Tilly. He had also obtained on his own terms the assistance of France, and was ready to enter upon his short but brilliant campaign. The campaign of Gustavus Adolphus.