ABSTRACT
Given the concentration of its population in a relatively small area, Japan would remain vulnerable to a first strike from China even if it acquired a small nuclear force. During the Second World War, the Japanese imperial army and navy pursued parallel nuclear-weapons programmes. The army's 'Project Ni' was based on the gas-diffusion method of uranium enrichment; the navy's 'Project F' focused on gas-centrifuge-enrichment technology. Government-sponsored studies on the desirability of indigenous nuclear weapons were again undertaken in the 1990s when the end of the Cold War, North Korea's nuclear quest and China's military modernisation changed Japan's security environment for the worse. In 1996, Japan was among the first to sign the Comprehensive Nuclear Test-Ban Treaty (CTBT), which it ratified the next year. Japan did not seek its own nuclear deterrent after China's 1964 nuclear test, nor after North Korea's 2006 test. Each time it had a better security option via US deterrence.
