History of germany

Lutherans from Scandinavia: 1625-1631

As a Lutheran monarch, the Danish king Christian IV has good cause to support Protestant states in north Germany under threat from Catholic neighbours. He is also eager to keep Catholics away from the Baltic. He has been promised a subsidy by England if he intervenes in Germany's wars. And he is interested in extending his own territory southwards to the estuaries of the Elbe and the Weser.

In May 1625 he marches into Germany. 
Christian IV is an unskilled commander, and he has the misfortune to have ranged against him the two most experienced generals of the age. Tilly commands the Bavarian army on behalf of the Catholic League. Wallenstein is at the head of the separate imperial army which he has raised for Ferdinand II.
Christian's first defeat is at the hands of Tilly, at Lutter in August 1626. Between them, Tilly and Wallenstein then drive the Danes north, clearing them from the Baltic coast, pursing them into the peninsula of Denmark and eventually confining Christian IV and his army to the Danish islands. 
By 1628 Wallenstein has been granted the duchy of Mecklenburg, and an army of his is besieging the town of Stralsund. If it falls to him, he will be master of the German Baltic coast. This dramatic increase in Catholic power, and in Wallenstein's personal standing, has several results of great significance for the next stage of the war.
A new surge of confidence causes Ferdinand II, in March 1629, to issue the Edict of Restitution. It demands that all Protestant land not specifically ceded in 1555 in the  peace of Augsburg be now returned to the Catholic church. This unilateral attempt to put the clock back eighty years is guaranteed to inflame the present religious conflict. 
The new Catholic presence on the shores of the previously Lutheran southern Baltic persuades the king of Sweden, Gustavus II, that he should enter the war. Resolving his long dispute with Poland (in the treaty of Altmark in September 1629), he brings an army across the sea and marches into Germany in July 1630.
Meanwhile the greatly increased stature of Wallenstein prompts the duke of Bavaria and the Catholic League to issue an ultimatum. Unless Ferdinand dismisses his general, he can expect no further cooperation. With reluctance, in August 1630, the emperor deprives an outraged Wallenstein of his high command. 
After Wallenstein's dismissal, Tilly becomes commander of the combined armies of the Catholic League and of the emperor against the intruding Swedes.
For a year the two opposing sides, Protestant and Catholic, fail to meet in direct battle. Each attempts to secure firm alliances among the many German principalities (Protestant princes are at this stage reluctant to commit themselves to the Swedish king). But eventually, at Breitenfeld near Leipzig in September 1631, there is a confrontation. It is Tilly's misfortune that this is the first public display of new tactics devised by Gustavus II. They prove devastating.