As commander of the Imperial armies, he won a series of victories, gaining the titles of Duke of Mecklenburg and 'General of the Baltic and Oceanic Seas'.

His goal was a large central European empire dominating both the Turks and western Europe. His ambition led to his dismissal in 1630, but he was reinstated to defend the empire against Swedish attack. He recovered Bohemia, but was defeated by Gustav II Adolph at Lutzen, and was again dismissed.

Wallenstein's intrigues with the Protestants alarmed the Catholic princes, and he was murdered in his bedroom at Eger by Irish mercenaries.