The Treaty of Stralsund (May 24, 1370) ended the war between the Hanseatic League and the kingdom of Denmark. The Hanseatic League reached the peak of its power by the conditions of that treaty.
The war began in 1361 with the capture of Visby, a hanseatic town on the island of Gotland, today belonging to Sweden. King Valdemar IV of Denmark took the town and declared it to be Danish. The Hanseatic League, which used to be rather a trade league than a political union, raised a fleet and blockaded the harbour of Copenhagen (1368). Denmark surrendered in 1369.
In the treaty the freedom of Visby was reestablished. Furthermore Denmark had to assure the Hanseatic League of free trade in the entire Baltic Sea. The league gained the right of participation in deciding the future heirs to the Danish throne.
See also: Stralsund