The Japanese program to develop nuclear weapons was conducted during World War II. Like the German nuclear weapons program, it suffered from an array of problems, and was ultimately unable to progress beyond the laboratory stage before the atomic bombings of Hiroshima and Nagasaki and the Japanese surrender in August 1945. Today, Japan's nuclear energy infrastructure makes it capable of constructing nuclear weapons at will. The de-militarization of Japan and the protection of the United States' nuclear umbrella have led to a strong policy of non-weaponization of nuclear technology, but in the face of nuclear weapons testing by North Korea, some politicians and former military officials in Japan are calling for a reversal of this policy. Background In 1934, Tohoku University professor Hikosaka Tadayoshi's "atomic physics theory" was released. Hikosaka pointed out the huge energy contained by nuclei and the possibility that both nuclear power generation and weapons could be created. In December 1938, the German chemists Otto Hahn and Fritz Strassmann sent a manuscript to Naturwissenschaften reporting that they had detected the element barium after bombarding uranium with neutrons; simultaneously, they communicated these results to Lise Meitner. Meitner, and her nephew Otto Robert Frisch, correctly interpreted these results as being nuclear fission and Frisch confirmed this experimentally on 13 January 1939. Physicists around the world immediately realized that chain reactions could be produced and notified their governments of the possibility of developing nuclear weapons. World War II The leading figure in the Japanese atomic program was Yoshio Nishina, a close associate of Niels Bohr and a contemporary of Albert Einstein. Nishina had co-authored the Klein–Nishina formula. Nishina had established his own Nuclear Research Laboratory to study high-energy physics in 1931 at RIKEN Institute (the Institute for Physical and Chemical Research), which had been established in 1917 in Tokyo to promote basic research. Nishina had built his first cyclotron in 1936, and another , 220-ton cyclotron in 1937. In 1938 Japan also purchased a cyclotron from the University of California, Berkeley. Due to the German Japanese alliance resulting from Germany's 4-Year-Plan, Japan and its military had already been pursuing nuclear science to catch up to the West in nuclear technology. This allowed for Nishina to introduce quantum mechanics to Japan. In 1939 Nishina recognized the military potential of nuclear fission, and was worried that the Americans were working on a nuclear weapon which might be used against Japan. In August