The Duchy of Holstein was established by a Scandinavian monarch under what union?
Duchy of Holstein The Duchy of Holstein (German: "Herzogtum Holstein" , Danish: "Hertugdømmet Holsten" ) was the northernmost state of the Holy Roman Empire, located in the present German state of Schleswig-Holstein. It was established when King Christian I of Denmark had his County of Holstein-Rendsburg elevated to a duchy by Emperor Frederick III in 1474. Holstein was ruled jointly with the Duchy of Schleswig by members of the Danish House of Oldenburg for its entire existence.
Magnus IV of Sweden Magnus IV (April or May 1316  – 1 December 1374; Swedish "Magnus Eriksson") was King of Sweden from 1319 to 1364, King of Norway as Magnus VII (including Iceland and Greenland) from 1319 to 1343, and ruler of Scania from 1332 to 1360. By adversaries he has been called "Magnus Smek" (English: "Magnus the Caresser").