Naval Battle of Fehmarn

This took place on 13 October 1644 north-west of the island of Fehmarn, now part of Germany, in the Baltic Sea.

A combined Swedish-Dutch fleet defeated a Danish fleet and took 1000 prisoners, including Ulfeld, Grabov and von Jasmund.

The Swedes had 16 ships with 392 guns, and the Dutch had 21 ships with 483 guns (making a total of 37 ships with 875 guns). The Danes had 17 ships with 448 guns. The Swedes expended two fireships and the Dutch lost one ship. The Danes lost 10 ships captured, including their largest three, and two wrecked.

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.