The Battle of Lützen, fought on 16 November 1632, is considered one of the most important battles of the Thirty Years' War. Led by the Swedish king Gustavus Adolphus, an Allied army primarily composed of troops from Sweden, Saxony, and Hesse-Kassel, narrowly defeated an Imperial force under Albrecht von Wallenstein. Both sides suffered heavy casualties, with Gustavus himself among the dead.
Wallenstein deployed his men in defensive positions, and the battle began with a series of frontal attacks by the Allied infantry. These nearly succeeded in breaking through before being repulsed with severe losses by Imperial cavalry under Pappenheim. Gustavus was killed as they fell back, but re-formed by his subordinates, his infantry overran the Imperial centre just before nightfall, supported by close range artillery fire. Wallenstein withdrew his remaining troops in good order, but was forced to abandon his wounded, many of his guns, and most of his supply train.
Despite the loss of their king, the Swedes continued the war under the direction of Axel Oxenstierna. Backed by French subsidies, in April 1633 Sweden formed the Heilbronn League with their German allies, and shortly afterwards defeated an Imperial army at Oldendorf. In February 1634, rumours that Wallenstein was about to change sides resulted in his assassination by Imperial agents.