The Services of Supply or "SOS" branch of the Army of the USA was created on 28 February 1942 by Executive Order Number 9082 "Reorganizing the Army and the War Department" and War Department Circular No. 59, dated 2 March 1942. Services of Supply became one of the three autonomous components of the Army of the United States on 9 March 1942. It was renamed the Army Service Forces on 12 March 1943, as it was felt that the term "supply" did not accurately describe its broad range of activities. From the day of inception (and even before) in 1942 through the end of WWII, the SOS/ASF was commanded by Lieutenant General (later General) Brehon B. Somervell.

Most theaters of war had their own logistical organization, usually also named the Services of Supply. The European Theater, and its SOS was subdivided into the ETO and the MTO (Mediterranean Theater of Operations) for the Operation Torch invasion of North Africa, then Sicily, then Italy, though the MTO was largely supplied by the SOS out of Great Britain. The SOS-ETO became TSF/ET (Theater Service Forces—European Theater) on D-Day, 6 June 1944, the term SOS was abolished, and its activities on the continent were referred to as COM-Z, or Communications Zone.