Like the Australians until late 1942, Imperial Japanese Army units tended to be recruited by region...
During the Kokoda phase of the Papuan campaign the majority of the Japanese fighting troops were from the island of Shikoku or from the Hiroshima area. Later these were reinforced by troops mainly from Osaka. The Imperial Japanese Navy escorted shipping to Papua and was engaged in coastal operations. Two thousand of the Navy's marines served at Buna and Milne Bay. The IJN (Imperial Japanese Navy) also provided almost all of the aircraft supporting land operations from bases at Lae, Gasmata and Rabaul. Perhaps 2100 of the Japanese force in Papua were not from Japan. These men, primarily engaged in carrying ammunition and food, were from Korea, China and Taiwan.