Waffen-SS and Wehrmacht
The Waffen-SS, the combat branch of the SS (the Nazi Party's paramilitary organization), became the de facto fourth branch of the Wehrmacht, as it expanded from three regiments to 38 divisions by 1945. Although the SS was autonomous and existed in parallel to the Wehrmacht, the Waffen-SS field units were placed under the operational control of the Supreme High Command of the Armed Forces (Oberkommando der Wehrmacht, OKW) or the Supreme High Command of the Army (Oberkommando des Heeres, OKH).
Competence struggles hampered organization in the German armed forces, as OKW, OKH, OKL (Luftwaffe had its own ground forces, including tank divisions) and Waffen-SS often worked concurrently and not as a joint command.
Read more about this topic: Wehrmacht