Frederick I (7 October 1471 – 10 April 1533) was the King of Denmark and Norway. His name is also spelled Friedrich in German, Frederik in Danish and Norwegian and Fredrik in Swedish. He was the ultimate Roman Catholic monarch to reign over Denmark, when subsequent monarchs embraced Lutheranism after the Protestant Reformation. As King of Norway, Frederick is most remarkable in never having visited the country and was never crowned King of Norway. Frederick was the younger son of the first Oldenburg King Christian I of Denmark, Norway and Sweden (1426–81) and of Dorothea of Brandenburg (1430–1495). 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 of Denmark. In 1490 at Frederick's majority, both duchies were divided between the brothers. 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 mercenaries took part. The expedition failed miserably, however, in the Battle of Hemmingstedt, where one third of all knights of Schleswig and Holstein lost their lives. When his brother, King John died, a group of Jutish nobles had offered Frederick the throne as early as 1513, but he had declined, rightly believing that the majority of the Danish nobility would be loyal to his nephew prince Christian. In 1523 Christian II, King of Denmark, Norway and Sweden, was forced by disloyal nobles to abdicate, and Frederick took the throne as King Frederick I. It is not certain that Frederick ever learned to speak Danish. After becoming king, he continued spending most of his time at Gottorp, a castle and estate in the city of Schleswig. In 1524 and 1525 Frederick had to suppress revolts among the peasants in Jutland and Scania who demanded the restoration of Christian II. The high point of the rebellion came in 1525 when Søren Norby, the governor (statholder) of Gotland, invaded Blekinge in an attempt to restore Christian II to power. He raised 8000 men who besieged Kärnan (Helsingborgs slott), a castle in Helsingborg. Frederick's general, Johann Rantzau, moved his army to Scania and defeated the peasants soundly in April and May 1525.

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