Polish–Swedish union

The Polish–Swedish union was a short-lived personal union between the Polish–Lithuanian Commonwealth, and the Kingdom of Sweden, when Sigismund III Vasa, King of Poland, was crowned King of Sweden in 1592. In 1599, after a civil war, he lost this crown and returned to Warsaw.

After the death of John III of Sweden, his son Sigismund became heir to the throne of Sweden. Sigismund at that time was already the elected King of Poland (since 1587). Sigismund certainly valued the Swedish throne and upon learning about the death of his father, and the pretensions to the throne of his uncle, Duke Charles of Södermanland, he asked the Sejm (Polish parliament) for permission to leave the Commonwealth and go to Sweden, where he could secure the Swedish crown. The Sejm gave him permission, and on 3 August 1593, Sigismund, accompanied by his wife, Anna of Habsburg, and other followers, departed for Sweden.

In Sweden, he encountered a serious problem due to his religion, as Sigismund was a devoted Catholic, and most of the Swedish population (including Charles) had converted to Lutheranism. There were fears that Sigismund, if elected king, would support the Catholics against the Protestants. At this period Duke Charles and his Protestant friends were clearly outnumbered by the supporters of Sigismund. Nevertheless, immediately after King John’s death, a synod summoned to Uppsala by Duke Charles rejected the new liturgy and drew up an anti-Catholic confession of faith, March 5, 1593. Holy Scripture and the three primitive creeds were declared to be the true foundations of Christian faith, and the Augsburg confession was adopted, on January 9, 1594, in Uppsala. Sigismund was confronted by the representatives of the Lutherans and the lower nobility. Pressured by the political situation, and amidst the turmoil which included Sigismund's Catholic entourage and their Lutheran opponents, he eventually agreed on February 19, to guarantee religious freedom to the Protestants, and forbade the Catholics from public demonstrations of their faith and from holding high offices.

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