During the Thirty Years' War, Sweden conquered approximately half of the Holy Roman states and defeated the Imperial army at the Battle of Breitenfeld in 1631. Gustav Adolphus planned to become the new Holy Roman Emperor, ruling over a united Scandinavia and the Holy Roman states, but he was killed at the Battle of Lützen in 1632. After the Battle of Nördlingen in 1634, Sweden's only significant military defeat of the war, pro-Swedish sentiment among the German states faded. These German provinces broke away from Swedish power one by one, leaving Sweden with only a few northern German territories: Swedish Pomerania, Bremen-Verden and Wismar. From 1643 to 1645, during the last years of the war, Sweden and Denmark-Norway fought the Torstenson War. The result of that conflict and the conclusion of the Thirty Years' War helped establish postwar Sweden as a major force in Europe.