The second phase of the Thirty Years’ War began in 1625. After the Battle of White Mountain, Spanish troops under Philip III had occupied part of the Palatinate in support of Ferdinand. German Protestant princes objected to the presence of these Spanish troops on German lands. The princes supported an invasion of Germany by the Protestant king Christian IV of Denmark, who was financed largely by the Dutch and the English. Christian was defeated, and in 1629 the victorious Ferdinand issued the heavy-handed Edict of Restitution, which ordered the return of all Catholic Church property seized by Protestants since 1552.

The third phase of the war began when the Lutheran king Gustav II Adolph of Sweden, who had long wanted to extend Swedish control over the Baltic, invaded Pomerania as the champion of the Protestant princes.

The Swedish army won a brilliant victory at Breitenfeld in 1631 and swept down to take Mainz and Prague. Following Gustav’s death on the battlefield in 1632 the war dragged on, accomplishing little but the devastation of the German countryside. In 1635 a truce was declared, and Ferdinand’s unpopular Edict of Restitution was revoked. In the fourth phase, the Catholic French, who wanted to undermine the Habsburgs, paid subsidies to the Protestant Swedish army to continue fighting. French troops also crossed the Rhine into German territories. After another 13 years of destruction, Emperor Ferdinand III and the princes were ready for peace. Encarta