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.
Olaf II of Denmark Olaf II Haakonsson (1370 – 23 August 1387) was King of Denmark as Olaf II (1376–1387) and King of Norway as Olaf IV (1380–1387). Olaf was son of King Haakon VI of Norway and the grandson of King Magnus IV of Sweden. His mother was Queen Margaret I of Denmark which made him the grandson of King Valdemar IV of Denmark. In addition to his claim on the thrones of Denmark and later Norway, he was in the direct succession line to the throne of Sweden (but for the interposition of Albert of Mecklenburg).