The war between the Hanseatic cities and Denmark between 1367 and 1370 and the Treaty of Stralsund concluding it have entered the public consciousness as the peak of the history of the Hanseatic League, although in reality, it looked different in many ways. The Hanseatic cities of Lower Saxony and Westphalia did not take part in the conflict, while there were some among the warring cities who were not members of the Hanseatic League, and even princes and kings joined the military alliance against Denmark. The study is about the causes of the armed conflict, the invasion of Gotland by Valdemar IV, King of Denmark, (22-27 July 1361), the response of most of the Hanseatic cities, the formation of the alliance of Greifswald (1 August 1361), joined by Magnus, King of Sweden and Haakon, King of Norway. The first war against Denmark brought the defeat of the alliance of Greifswald (1362-1364), but the new anti-Valdemar coalition established with the Confederation of Cologne (1367) won a significant victory in the subsequent war, which Denmark recognised in the Treaty of Stralsund (24 May 1370)
