Reising M55 Submachine Gun

When the US entered WWII, submachine guns were in short supply and high demand. Much of the production of Thompson guns was being purchased by the UK, and what guns were available to the US military went first to the Army. In accordance with long tradition, the Marine Corps were secondary to the Army in receiving new weapons. However, the formation of a Marine paratroop unit in particular necessitated the Corps finding *some* sort of suitable submachine gun. What was