Treaty of Copenhagen

The Treaty of Copenhagen concluded the Second Northern War between Sweden and Denmark-Norway. King Charles X Gustav of Sweden had won sweeping victories, including a daring march across the frozen Belts in 1658 that forced Denmark into the harsh Treaty of Roskilde. When Charles renewed the war and attempted to conquer Denmark outright, Danish resistance and foreign intervention checked his ambitions.

Signed in 1660, the Treaty of Copenhagen revised the earlier settlement and restored peace between the two kingdoms. Sweden retained the rich provinces of Scania, Halland, and Blekinge on the southern Scandinavian peninsula, confirming its possession of formerly Danish lands. Denmark, however, recovered the island of Bornholm and the Norwegian province of Trondheim, which it had been forced to cede at Roskilde.

The treaty established a frontier between Sweden, Denmark, and Norway that has largely endured to the present day, fixing the modern boundaries in the Scandinavian peninsula. It marked the height of Swedish territorial power in the region while securing Denmark's survival as an independent kingdom. The settlement brought a lasting stability to the long contest for dominance over the Baltic approaches.