The Polish–Swedish War (1617–18) was a phase of the longer Polish–Swedish War of 1600 to 1629. It continued the war of 1600–11 and was an attempt by Sweden to take Polish pressure off Russia. The Polish–Lithuanian Commonwealth was then also fighting Tartars and (on the southern front) the Ottoman Empire. Russia and Sweden were at that stage allied, prior to the Ingrian War, part of the Polish–Muscovite Wars. The 1617–18 war's cause was a dispute over Livonia and Estonia, and a dispute between Sigismund III Vasa and Charles IX of Sweden over the Swedish throne.