Outnumbered and with many inexperienced troops, Tilly built defensive works along the River Lech, centred on the town of Rain, hoping to delay Gustavus long enough for Imperial reinforcements under Albrecht von Wallenstein to reach him. On 14 April, the Swedes bombarded the defences with artillery, then crossed the river the next day, inflicting nearly 3,000 casualties, including Tilly. On 16th, Maximilian of Bavaria ordered a retreat, abandoning his supplies and guns.

The Battle of Rain took place on 15 April 1632 near Rain in Bavaria. It was fought by a Swedish-German army under Gustavus Adolphus of Sweden, and a Catholic League force led by Johann Tserclaes, Count of Tilly. The battle resulted in a Swedish victory, while Tilly was severely wounded and later died of his injuries.

Despite this victory, the Swedes had been drawn away from their bases in Northern Germany and when Maximilian linked up with Wallenstein found themselves besieged in Nuremberg. This led to the largest battle of the war on 3 September, when an assault on the Imperial camp outside the town was bloodily repulsed.