Requests for designs, at various stages during the war, were made to the major German aircraft manufacturers (Messerschmitt, Junkers, Focke-Wulf and the Horten Brothers) early in World War II, coinciding with the passage of the Destroyers for Bases Agreement between the United States and the United Kingdom in September 1940. Heinkel's bid for the project had occurred sometime shortly after February 1943, by which time the RLM had issued the Heinkel firm the airframe type number 8-277[3] for what essentially became its entry.