Battle of Jüterbog
Field Marshal Lennart Torstenson had unexpectedly marched into Jutland in September 1643.
While engaged in operations there, an Imperial army under the command of Count Matthias Gallas ventured north towards Jutland to trap the Swedish army there and destroy it. However, Torstensson turned his army around and headed south towards Gallas' approaching host.
Christian IV of Denmark had been drawing closer to his former Habsburg foes. He was entertaining the idea of entering the war on the Imperial side, which would have placed the Swedes in a perilous position. Oxenstierna determined to strike first.
The main Swedish field army under Torstensson was besieging Brünn (Brno) in Moravia. On 2 September, 1643, at Oxenstierna’s command, they suddenly retreated across the breadth of Germany. On 22 December, 1643 they began to advance up the Jutland peninsula. Christian was no more able to stop the Swedish veterans than he had been able to stop Tilly’s forces nearly a decade before.
The Emperor called Gallas to bring the Imperial forces in Bohemia westward to aid Christian. Gallas did not march west until the autumn of 1644 and, upon his juncture with the Danes at Kiel, lay utterly inert.
The loss of Jutland, combined with attacks against the areas of Denmark bordering Sweden and naval attacks by a powerful fleet the Dutch were persuaded to provide, proved too much for the Danes. In November, 1644, an armistice was signed with the Swedes.
Gallas' army had initially been sent to Jutland by Emperor Ferdinand III to aid Denmark in combating the Swedish invasion. When Rákóczy's army, in alliance with Sweden, had begun an offensive on Habsburg Hungary in February 1644, Ferdinand III felt it necessary to recall Gallas to Hugary's aid. The battle of Juterbog occured within this context.
Torstensson took advantage of the Imperial retreat by routing Gallas' forces through the most devastated possible areas, causing the vast majority of his men to die of starvation.
This episode was a key event not only in Denmark's exit from the Thirty Years' War, but also its decline in the face of a rising Sweden.
Gallas was dismissed shortly thereafter.