Universal History Annotation << Back On the Japanese Attempts to Make Atomic Bomb in 1940-ies Samkharadze T.G., Gorobets B.S. This paper presents a sort of summary of foreign and Russian publications on the attempts to make uranium bomb in Japan, during the Second World War. There were several physicists of world class in Japan: Т. Hagivara, I. Nisina, R. Sagane, Ts. Asada, B. Arakatsu, М. Киkuchi. They knew well of the recent key achievements in nuclear physics that meant that, generally speaking, it was possible to make atomic bomb with the charge of uranium-235. In the spring of 1940, prof. Sagane made an account on the nuclear problem, in whole, for the Army commandment. His conclusion was that, in principle, making a nuclear bomb of enormous power was achievable for Japan. In the end of 1942, Nisina began lead «Ni-Project» in the Institute of Physical and Chemical researches (RIKEN), in Tokio. In may 1943, prof. Nisina made a report with his estimation that making an atomic bomb would require 1 kg of uranium-235, it was equivalent of 18 thousand t. TNT. The most diffi cult problem was to separate uranium isotopes-235 and 238. In parallel, the Navy commandment charged prof. B.Arakatsu to head so-called “F-Project” (F meant fission). But the scale of the both projects was scanty compared to the giant goal. About 15 specialists were engaged in «Ni-Project». Even less than that were in «F-project». Nevertheless, the RIKEN group managed to mine 150 t of uranium ore in Japan, Korea and Malaya. They extracted out of it as much as 300 kg U3 O8 that contained 1,8 kg of uranium-235. The Japanese built a centrifuge machine to separate isotopes-235 and 238 in form of uranium hexafluoride gas. But they needed several thousand of such centrifuges. In fact, they had to build up atomic industry. Without it making even one uranium bomb was impossible. Meanwhile the summary financing of the both projects was equivalent of 650 thousand dollars. It was 3 thousand times less than costs of American-English Manhatten project. It seems that Soviet intelligent agents knew about the nuclear attempts of Japan. However we could not fi nd any traces of response of the Soviet top chiefs to it. After the atomic bombardment of Hiroshima and Nagasaki, 6 and 9 of august 1945, the Japanese were informed that the third atomic bomb would be thrown down, possibly upon Tokio, if the Empire not surrender. The capitulation of Japan was declared 2 September 1945. Кeywords: Japanese аtomic project, Japanese uranium ores, uranium-235, Iosio Nisina, Bunsaku Arakatsu, capitulation of Japan. DOI: 10.25791/vseist.03.2025.1230 Pp. 15-24.