At the unsuccessful assault on Albrecht von Wallenstein's camp at the Alte Veste, Banér received a wound, and soon afterwards, when Gustavus marched towards Lützen, was left in command in the west, where he was opposed to the imperial general Johann von Aldringen. Two years later, as Swedish field marshal, Banér, with 16,000 men, entered Bohemia and, combining with the Saxon army, marched on Prague. But the complete defeat of Bernard of Saxe-Weimar in the first Battle of Nördlingen stopped his victorious advance.