Charles X (king of Sweden)
Charles X, 1622–60, king of Sweden (1654–60), nephew of Gustavus II. The son of John Casimir, count palatine of Zweibrücken, he brought the house of Wittelsbach to the Swedish throne when his cousin, Queen Christina, abdicated in his favor. Before his accession, Charles had gained both military and diplomatic experience, fighting under Torstensson in the Thirty Years War and serving under Chancellor Oxenstierna. As king, Charles remedied Christina's loss of crown lands by securing their restitution at the Riksdag of 1655. He reopened hostilities with Poland and took Warsaw and Kraków in 1655, but Polish resistance became formidable after the heroic and successful defense of Częstochowa. Charles's position deteriorated quickly. Czar Alexis of Russia invaded Livonia, Frederick III of Denmark declared war (1657) on Sweden, and Frederick William of Brandenburg deserted his alliance with Sweden. Charles hastened to Denmark, crossed the frozen sea to threaten Copenhagen, and forced the Danes to make peace. By the Treaty of Roskilde (1658) Sweden's southern boundary was extended to the sea; Denmark ceded to Sweden the provinces of Skåne, Halland, Blekinge, and Bohuslan and also Bornholm and part of Norway. Denmark's refusal to renounce an alliance with the Netherlands caused Charles to resume the war in 1658. England, the Netherlands, and France intervened in favor of Denmark. Charles, after concluding a truce with Russia (1658), began to negotiate for a general peace. He died suddenly before the negotiations were ended and was succeeded by his son, Charles XI. His wars were settled to the advantage of Sweden. By the Treaty of Copenhagen (1660) Sweden regained its four southern provinces from Denmark, and by the Treaty of Kardis (1661) with Russia the two countries returned to the prewar status quo. (For the settlement with Poland, see Oliva, Peace of.) During Charles's reign Sweden lost New Sweden in America to the Dutch.