Sweden, also known as the Swedish Empire or the Kingdom of Sweden, was one of the great European nations of Northern Europe in the Scandinavian Union. It first existed in 1561 after the Swedish conquest of Estonia. At its height, it also included Finland. However, in 1721, Sweden was forced to cede large lands in Estonia and southeastern Finland to Russia. An era known as the Stormaktstiden (which literally means "the Great Power Era”), occurred when the country was at the height of its power. The “start” of the empire has said to be 1611, when Gustavus Adolphus claimed the throne till the end of 1718, when Charles XII died and the Great Northern War between Russia and Sweden ended. An increase of political power and territory occurred as part of the terms of the Peace of Westphalia that allowed Sweden to reach the height of its power.
After Gustavus Adolphus died in 1632, the empire was often controlled by the high nobility, especially the Oxenstierna family, acting as the main driving force of the country. Like many other central and eastern European countries, feudalism still existed, especially the tradition of serfdom (only in Estonia and the Swedish portions of the Holy Roman Empire) and the equality in status of Swedish estates endorsed by kings and peasants alike. However, the Great Reduction of 1680 forced the nobility to return their estates to the Swedish crown. Yet serfdom still remained a strong force in the territories in Estonia and the Holy Roman Empire.
After Sweden emerged victorious after the Thirty Years’ War, the height of Stormaktstiden was reached during the Second Northern War. However, its primary adversary Denmark was neutralized according to the Treaty of Roskilde in 1658. During the Scanian War, Sweden (with French support) was able to maintain itself. Charles XI of Sweden brought back the empire into a period a peace, until Russia, Denmark, and Saxony attacked his successor, Charles XII. After emerging victorious, Charles controlled the empire after the Peace of Travendal in 1700 and the Treaty of Altranstädt in 1701. However, the Battle of Poltava in 1709 brought the Stormaktstiden period to end.
Attempting re-establish Swedish control of the Baltic region, it allied with the coalition against its traditional ally France in the Napoleonic Wars. However, Charles XIII was bribed by Napoleon to join his side, which was successful. Later, in 1831, Napoleon’s sister married the king, incorporating Sweden into France.