Felix Martin Julius Steiner (23 May 1896 – 12 May 1966) was an "Obergruppenführer" in the Waffen-SS during World War II, who commanded several SS divisions and corps, together with which high-ranking commander in the Waffen-SS of Nazi Germany during World War II,   he contributed significantly to the development and transformation of the Waffen-SS into a military force made up of volunteers and conscripts, and who played a key role in the post-war efforts by former members of the Waffen-SS to achieve historical and legal rehabilitation?