On February 24, 1938, a Japanese manufacturer, Mitsui (a subsidiary of Nakajima Hikoki), purchased the production rights and technical data to the DC-3 for $90,000. Unknown to the United States at the time, the sale was directed behind the scenes by the Imperial Japanese Navy (who was planning on using the type in the invasion of the East Indies). They saw the potential in the DC-3 to serve as a military transport. Mitsui and Showa Hikoki, another manufacturer, made many engineering revisions to take advantage of standard Japanese parts and raw materials. Japan also purchased and imported some machinery from the U.S. to speed up production. The first Japanese-produced DC-3 appeared in September 1939. By May 1941, the fifth DC-3 left the Showa factory, this one using the last Douglas-built fuselage. By July 1941, the factory was producing one DC-3 transport per month, far short of the one airplane per day demanded by the Imperial Japanese Navy.71 Finally by 1942, the production quota was reached. (See Appendix H.)
Although ostensibly purchased for civilian use, the Japanese DC-3s were given a Navy designation L2D2 (L-transport, 2-second Navy type, D2-second Douglas design). L2D1 became the designation for imported DC-3s. The Japanese built eight separate sub types in two basic configurations, straight airline type, and cargo planes.
Japan modified the transport design for easier production. In addition, they replaced the Pratt & Whitney 1,000 hp engines they imported with 1,000 hp Mitsubishi Kinsei 43 radial engines.
After two years of manufacture, Nakajima had built 71 C-47 type aircraft (designated L2D2 Navy Type 0 Transport Model 11) and switched to manufacturing combat aircraft. Meanwhile, Showa built 416 DC-3 type aircraft, including 75 cargo versions with the "barn door" and reinforced floor (designated L2D2-1). The first Japanese military version with wide cargo doors, remarkably similar to the U.S. C-47, appeared about the same time as the C-47. There are strong suspicions that it was a copy, and not the product of an independent design. The Japanese manufactured 75 cargo versions of the DC-3.