Charles X (1622-1660) of Sweden became king in 1654 when Queen Christina gave up the throne. He was the nephew of King Gustavus Adolphus. While Charles was king, Sweden suffered from serious financial and social problems. But Charles could pay only limited attention to these matters because the country was at war during most of his reign. From 1655 to 1657, he fought a largely indecisive war in Poland. In 1657, Denmark, Poland’s ally, declared war on Sweden. Charles quickly defeated Denmark. In 1658 in the Treaty of Roskilde, Denmark gave Sweden territories in what are now Sweden, Denmark, and Norway. This treaty marked the high point of Sweden’s Baltic empire. Later in 1658, faced by a coalition of Poland, Russia, Prussia, and Denmark, Charles attacked Denmark again. He died during this conflict, probably of pneumonia, on Feb. 13, 1660. Charles was born on Nov. 8, 1622, in Nyköping, Sweden.
