Polish–Swedish union
The Polish–Swedish union was a short-lived personal union between the Polish–Lithuanian Commonwealth and the Kingdom of Sweden between 1592 and 1599. It began when Sigismund III Vasa, elected King of Poland and Grand Duke of Lithuania, was crowned King of Sweden following the death of his father John III. The union ended following a civil war in Sweden in which he lost the crown to his uncle, who eventually became Charles IX. Sigismund afterwards returned to Warsaw and pursued a war against his former realm.