The Duchy of Holstein was established by a Scandinavian monarch under what union?
Christian I of Denmark Christian I (February 1426 – 21 May 1481) was a Scandinavian monarch under the Kalmar Union. He was King of Denmark (1448–1481), Norway (1450–1481) and Sweden (1457–1464). From 1460 to 1481, he was also Duke of Schleswig (within Denmark) and Count (after 1474, Duke) of Holstein (within the Holy Roman Empire). He was the first Danish monarch of the House of Oldenburg.
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.