Under what union did the king who created Duchy of Holstein serve?
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. Christian I of Denmark: Christian I (February 1426 – 21 May 1481) was a Scandinavian monarch under the Kalmar Union.
i don't know