In April 1942, Adolf Hitler made the production of aerial torpedoes a German priority, and the "Luftwaffe" took the task over from the "Kriegsmarine". The quantity of available aerial torpedoes outstripped usage within a year, and an excess of aerial torpedoes was on hand at the end of the war. From 1942 to late 1944, about 4,000 aerial torpedoes were used, but some 10,000 were manufactured during the whole war. Torpedo bombers were modified Heinkel He 111 and Junkers Ju 88 aircraft, but the Focke-Wulf Fw 190 fighter aircraft was successfully tested as a delivery system. Deficiencies in German-designed torpedoes after the capitulation of Italy in September 1943 were addressed just over a year before, through the "yanagi" visit of Japanese submarine "I-30" in August 1942, to supply the Wehrmacht with the Type 91 torpedo's technology and blueprints, to be made in Germany itself as the Lufttorpedo LT 850.