The Battle of Kunersdorf, fought in the Seven Years' War, was Frederick the Great's most devastating defeat. On August 12, 1759, near Kunersdorf (Kunowice), east of Frankfurt (Oder), 50,900 Prussians were defeated by a combined allied army 65,000 strong consisting of 41,000 Russians and 24,000 Austrians under Pyotr Saltykov.