The naval battle at Fehmarn was a pivotal moment in the continuing conflict involving Sweden, the Dutch Republic, and Denmark during the Thirty Years' War. The alliance between Sweden and the Dutch Republic was bolstered by mutual interests in controlling trade routes and expanding their territorial influence across the Baltic Sea. In this particular instance, the combined naval forces launched an offensive against the Danish fleet, which had previously maintained dominance in these waters. The battle commenced on October 13, and after intense fighting, the Swedish-Dutch alliance emerged victorious. The extent of the victory was underscored by the capture of approximately 1,000 Danish sailors who were taken as prisoners of war, greatly weakening Denmark's naval capabilities. Significant commanders, likely including Swedish Admiral Claes Hinderchijn and Dutch Admiral Witte Corneliszoon de With, played critical roles in orchestrating the tactics that led to the Danish defeat. The victory not only showcased the military prowess of the Swedish-Dutch alliance but also served to reinforce their dominance in the Baltic region.

As a result of this battle, the Danish fleet faced considerable losses, leading to a precarious situation for Denmark, which was already strained from ongoing military engagements. The aftermath saw heightened tensions in the region as both Sweden and the Dutch aimed to exploit their newfound advantage at sea. This battle highlighted the strategic importance of naval power during this era as well as the significance of alliances in achieving military objectives.