The war against Sigismund () was a war between Duke Charles, later known as King Charles IX of Sweden, and Sigismund, who was at the time the king of both Sweden and the Polish–Lithuanian Commonwealth (that is, the King of Poland and the Grand Duke of Lithuania). Lasting from 1597 to 1599, it is also called the War of Deposition against Sigismund, since the focus of the conflict was the attempt to depose the latter from the throne of Sweden. The war eventually resulted in the deposition of Sigismund (with Duke Charles taking over the government and later also acceding to the throne), the dissolution of the Polish–Swedish union, and the beginning of an eleven-year war.
Background
thumb|The Polish-Swedish Union in question
When Stephen Báthory died in 1586, Sigismund Vasa, son of King John III and Catherine Jagiellonica, was elected king of the Polish–Lithuanian Commonwealth in an attempt to continue the Polish–Swedish alliance, the original purpose being to confront Ivan IV "the Terrible" of Russia. Then conflicts arose. Duke Charles, the only living son of Gustav Vasa, did not approve the accession of Sigismund, his nephew and a Catholic, to the government of a realm that could just as well be his.