In 1639, however, he again overran northern Germany, defeated the Saxons at Chemnitz and invaded Bohemia itself. The winter of 1640–1641 Banér spent in the west. His last achievement was an audacious "coup de main" on the Danube. Breaking camp in mid-winter (a very rare event in the 17th century) he united with the French under the Comte de Guébriant and surprised Regensburg, where the Diet was sitting. Only the break-up of the ice prevented the capture of the place. Banér thereupon had to retreat to Halberstadt. Here, on 10 May 1641, he died, possibly due advanced liver cirrhosis caused by his excessive alcohol consumption, after designating Lennart Torstenson as his successor. He was much beloved by his men, who bore his body with them on the field of Wolfenbüttel. On the other hand, the enemies of Sweden rejoiced and even a parody requiem hoping that he was burning in hell was composed in Bohemia that was badly pillaged by Banér. He was buried at the Riddarholmen Church in Stockholm.