The Polish–Ottoman War (1620–21) forced Poland to withdraw from Moldavia in southeastern Europe, but Sigismund's victory over the Turks at Khotyn diminished the supremacy of the Sultanate and eventually led to the murder of Osman II. This secured the Turkish frontier for the duration of Sigismund's rule. In spite of the victories in the Polish–Swedish War (1626–1629), the exhausted Commonwealth army signed the Treaty of Altmark which ceded much of Livonia to Sweden under Gustavus Adolphus. At the same time, the country's powerful parliament was dominated by nobles ("Pic. 2") who were reluctant to get involved in the Thirty Years' War; this neutrality spared the country from the ravages of a political-religious conflict that devastated most of contemporary Europe.