 After Nyborg had been taken by a Dutch-Danish force, the Danish Isles were abandoned by the Swedes.Negotiations were opened and the Treaty of Copenhagen was signed on May 27, 1660, and it marked the conclusion of the Second Northern War between Sweden and the alliance of Denmark and the Polish-Lithuanian Commonwealth.In conjunction with the Treaty of Roskilde, it ended a generation of warfare and established the present-day borders of Denmark, Norway and Sweden.