Although the battle took place near Allenstein , it was named after Tannenberg by the Germans , because they wanted to express that they had made good their defeat at the medieval Battle of Tannenberg or ( Grunwald ) . Ludendorff sent the official dispatch from Tannenberg , and the battle was named Battle of Tannenberg at the direct request of Hindenburg . Hindenburg chose Tannenberg because of its historical significance ; it was the location where the Teutonic Knights were defeated by the joint forces of the Kingdom of Poland and the Grand Duchy of Lithuania at the Battle of Grunwald ( referred to in German as Schlacht bei Tannenberg â '' `` Battle of Tannenberg '' ) .