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.
Union of Kėdainiai Union of Kėdainiai (or Agreement of Kėdainiai, Polish: "Umowa Kiejdańska") was an agreement between several magnates of the Grand Duchy of Lithuania and the king of the Swedish Empire, Charles X Gustav. It was signed on 20 October 1655 during the "Swedish Deluge", part of the Second Northern War. In contrast to the preceding Treaty of Kėdainiai of 17 August, which put Lithuania under Swedish protection, the purpose of the Swedish-Lithuanian union was to end Lithuania's union with Poland, and set up two separate principalities in the Grand Duchy of Lithuania. One of these was to be ruled by the Radziwiłł ("Radvila") family, while the rest of the duchy was to remain a Swedish protectorate.