Sigismund III Vasa, born on 20 June 1566, was the son of King John III of Sweden and Catherine Jagiellon. He became King of Poland and Grand Duke of Lithuania in 1587 and King of Sweden from 1592 to 1599. He was the first monarch from the House of Vasa. Sigismund sought to unify Poland and Sweden under Catholicism, leading to conflicts with Protestant factions in Sweden, which resulted in his deposition in 1599.Sigismund's reign was marked by efforts to consolidate power, often undermining parliamentary authority. He promoted Catholicism, granting privileges to the Jesuits during the Counter-Reformation. His military campaigns included a successful invasion of Russia during the Time of Troubles, resulting in the capture of Smolensk and Moscow, marking Poland's greatest territorial expansion. However, his conflicts with Sweden ended unfavorably, leading to territorial losses in Livonia.Born at Gripsholm Castle, Sigismund was raised as a Catholic despite the Protestant political climate in Poland. He was educated in multiple languages and was influenced by his mother's Catholicism. After his election as king, he faced opposition from the Polish nobility, particularly from Chancellor Jan Zamoyski, who criticized his ties to the Habsburgs and his attempts to centralize power.Sigismund's marriage to Anne of Austria in 1592 was initially well-received, but her death in 1598 deeply affected him. He later married Constance of Austria, which further fueled opposition among the nobility. His reign saw the Zebrzydowski rebellion in 1606, a response to his attempts at absolute rule, which ultimately failed but highlighted the growing discontent among the nobility.During the Polish–Swedish War, Sigismund's ambitions to reclaim the Swedish throne led to civil war in Sweden, where Duke Charles IX emerged as a rival. Sigismund's military campaigns in Russia during the early 17th century were initially successful but ultimately led to a costly and protracted conflict. The Truce of Deulino in 1618 granted Poland new territories but failed to secure lasting control over Russia.Sigismund's involvement in the Thirty Years' War was limited by the Polish parliament's refusal to engage militarily. His reign also included conflicts with the Ottoman Empire, culminating in the Polish–Ottoman War, where Polish forces faced significant challenges. Despite military successes, his reign was characterized by internal strife and religious persecution against Protestants and other minorities.Sigismund died on 30 April 1632, after a prolonged illness. His reign is often viewed as a period of cultural and architectural development, but also marked by political intrigue and religious intolerance. His legacy includes the establishment of Warsaw as the capital of Poland and significant contributions to the arts and architecture.