Editing Frederick I of Denmark (section)

==Background==
Frederick was the younger son of the first Oldenburg King [[Christian I of Denmark]], Norway and [[Sweden]] (1426–81) and of [[Dorothea of Brandenburg]] (1430–95).  Soon after the death of his father, the underage Frederick was elected co-Duke of [[Schleswig]] and [[Holstein]] in 1482, the other co-duke being his elder brother, King [[John, King of Denmark|John of Denmark]]. In 1490 at Frederick's majority, both duchies were divided between the brothers.<ref>{{citation | publisher = Runeberg | language = da | url = https://runeberg.org/salmonsen/2/8/0865.html | contribution = Frederik I, Konge i Danmark og Norge | title = Salmonsens konversationsleksikon}}.</ref>

In 1500, he had convinced his brother King John to conquer [[Dithmarschen]]. A great army was called from not only the duchies, but with additions from all of the [[Kalmar Union]] for which his brother briefly was king. In addition, numerous German [[mercenary|mercenaries]] took part. The expedition failed miserably, however, in the [[Battle of Hemmingstedt]], where one-third of all [[knight]]s of Schleswig and Holstein lost their lives.<ref>{{cite web|url=   https://runeberg.org/salmonsen/2/6/0247.html|title= Ditmarsken (Dithmarschen, "de tyske Marsklande") |publisher = Salmonsens konversationsleksikon |access-date= August 15, 2016}}</ref>