In February 1632, the Saxons attacked the Bavarian town of Bamberg with an army of German recruits. The Imperialists marched with 22,000 men under Tilly and recaptured the town in March. The force was too weak to exploit this situation, however, and retreated to Ingolstadt, which controlled a major bridge over the Danube River. This Imperialist success led Adolphus to abandon plans to invade Austria and instead moved into Bavaria in an attempt to bolster the morale of his German allies. Troops from Saxe-Weimar joined his army, totalling 37,000 men and 72 guns.
At the end of March, the Swedes entered Nuremberg and were nearing the defensive line established by the Imperialists along the Lech River. The main Imperial army had entrenched and fortified the town of Rain, leaving a small force covering Augsburg.
