The Thirty Years War consisted of multiple phases, lasting from 1618 to 1648. The initial phase, what historians refer to as the Bohemian Revolt, was a result of the Holy Roman Emperor, Ferdinand II, attempting to assert imperial and Catholic control over territories that had broken away during the Reformation. The result of imperial aggression led to the “German” phase that resulted in the intervention of Spain, supporting their Catholic allies. In 1625, the Danes intervened to support the Protestants. The move proved disastrous for the Danes. Following their defeat in the Battle of Lutter, the Catholic forces under the command of Albrecht von Wallenstein marched against Denmark, occupying the Jutland peninsula. The “Danish” phase ended in 1629 with the Treaty of Lubeck, which saw Denmark cede support of its Protestant allies. With the Protestant cause nearing collapse, a desperate measure was needed. This came in the form of Gustav Adolphus and his Swedish army.
The “Swedish” phase occurred in 1630, with the Swedish invasion of the Holy Roman Empire. The Swedish intervention was a major turning point for the Protestant cause. With a strong, well-trained army, the Swedes swept across the Holy Roman Empire, liberating Protestant territories lost to the Catholic forces. In 1631, Gustav achieved a decisive victory over the Catholics in the Battle of Breitenfeld. The victory strengthened Gustav’s position in northern Germany, and inspired other Protestant territories to join the Swedish cause.
The Swedes continued their aggressive campaign against imperial forces, and in the Battle of Rain, the Count of Tilly (one of the empire’s greatest generals) was mortally wounded by Swedish forces. In response to the loss of Tilly, Ferdinand II recalled Wallenstein from retirement. In November 1632, Gustav and Wallenstein would face off in the Battle of Lutzen. The results of the battle would have lasting consequences on the Protestant movement.
Plagued by heavy fog, the two sides did not clash until 11 a.m. The Swedish forces gained the upper hand early in the battle, flanking Wallenstein’s left wing of his army. To counter the assault, Count Gottfried von Pappenheim led a cavalry charge that stalled the Swedish advance, but was mortally wounded in the action. Hours later, Gustav would lead his own cavalry charge against the imperial lines. Lost in the chaos of smoke and fog, Gustav would be killed in the attack. Despite the loss of their king, the Swedish forces were triumphant. With the death of the Swedish king, the Protestants lost their most successful commander. Sweden would remain in conflict until the Peace of Prague treaty in 1635.