Dutch–Swedish War

The Dutch-Swedish War (1658–1660), was a Dutch intervention in the Northern Wars, in which Sweden tried to extend its control over the Baltic Sea. To the Dutch, the Baltic trade was vital, both in quantity and quality. They had always been able to convince Denmark by threat of force to keep the Sound tolls at a low level but they feared a strong Swedish empire might not be so complying.

When Charles X of Sweden had been unable to continue his hold on Poland – partly because the Dutch fleet relieved the besieged city of Danzig in 1656 – he turned his attention on Denmark, invading that country from what is now Germany. He broke the Treaty of Roskilde with Frederick III of Denmark and laid siege to Copenhagen. In 1658, the Dutch sent an expedition fleet of 75 ships, 3,000 cannon and 15,000 troops; in the Battle of the Sound it defeated the Swedish fleet and relieved Copenhagen. In 1659, the Dutch liberated the other Danish isles, once more guaranteeing the essential supply of grain, wood, and iron from the Baltic region.