High Quality Content by WIKIPEDIA articles! The Battle of Kunersdorf, fought in the Seven Year`s 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 59,500 strong consisting of 41,000 Russians and 18,500 Austrians under Pyotr Saltykov. Only 3,000 soldiers from original 50,900 Prussian army returned to Berlin after the battle, though many more had only scattered.