The 11th SS Panzer Army was an undermanned German panzer army that existed from 26 November 1944 to 21 April 1945. The army was formed by Army Group Vistula commander Heinrich Himmler, and it was corps-sized, but Himmler liked the sound of "army" better than "corps", so he gave command of the weakened army to Felix Steiner. The army took part in the Operation Solstice counterattack along the Oder River in February 1945, and the army was weakened when many of its units were sent to join the 3rd Panzer Army, while the remaining units were sent to fight the Western Allies. What was left of the army defended the Weser River and the Harz Mountains, and it surrendered to the Western Allies on 21 April 1945; Army Detachment Steiner replaced it.