If it really wanted to, Japan could have one in as little as three months and likely has already been working on them.

A TNI Video Interview: Are America’s nuclear forces the right size? Should Japan consider acquiring its own nuclear weapons? We ask Yale Grand Strategy Fellow Christine M. Leah.
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America’s policy of opposing the proliferation of nuclear weapons needs to be more nuanced. What works for the United States in the Middle East may not in Asia. We do not want Iran or Saudi Arabia to get the bomb, but why not Australia, Japan, and South Korea? We are opposed to nuclear weapons because they are the great military equalizer, because some countries may let them slip into the hands of terrorists, and because we have significant advantage in precision conventional weapons. But our opposition to nuclear weapons in Asia means we are committed to a costly and risky conventional arms race with China over our ability to protect allies and partners lying nearer to China than to us and spread over a vast maritime theater. Continue reading