Sigismund III Vasa

Sigismund III Vasa (Polish: Zygmunt III Waza, Lithuanian: Žygimantas Vaza; 20 June 1566 – 30 April 1632

N.S.) was King of Poland and Grand Duke of Lithuania from 1587 to 1632 and, as Sigismund, King of Sweden from 1592 to 1599. He was the first Polish sovereign from the House of Vasa. Zealously religious, he imposed Catholicism across the vast realm, and his crusades against neighbouring states marked Poland's largest territorial expansion. A deeply polarising ruler, he presided over the end of the Golden Age of prosperity and achievement, further distinguished by the transfer of the country's capital from Kraków to Warsaw.

Sigismund was the son of King John III of Sweden and his first wife, Catherine Jagiellon, daughter of King Sigismund I of Poland. Elected monarch of the Polish–Lithuanian Commonwealth in 1587, he sought to unify Poland and Sweden under one Catholic kingdom, and when he succeeded his deceased father in 1592, the Polish–Swedish union was created. Opposition in Protestant Sweden caused a war against Sigismund headed by Sigismund's uncle Charles IX of Sweden, who deposed him in 1599.

Sigismund attempted to hold absolute power in all his dominions and frequently undermined parliament. He suppressed internal opposition, strengthened Catholic influence and granted privileges to the Jesuits, whom he employed as advisors and spies during the Counter-Reformation. He actively interfered in the affairs of neighbouring countries; his successful invasion of Russia during the Time of Troubles resulted in the seizure of Smolensk and occupation of Moscow, resulting in Poland's historical greatest territorial extent. Sigismund's army also defeated the Ottoman forces in southeastern Europe, which hastened the downfall of Sultan Osman II. However, the Polish–Swedish conflict had a less favourable outcome. After a series of skirmishes ending in a truce, King Gustavus Adolphus of Sweden launched a campaign against the Commonwealth and annexed parts of Polish Livonia.