South Korea would very likely arm themselves with nuclear weapons, as would Japan if they felt sufficiently threatened. The U.S. is a long ways away and is always going to be perceived as having other interests as well. These countries are going to want their own arsenal that they have direct control over rather than relying on the discretion of the United States.

This isn't the best source (the age), but here are a few choice quotes:
Mr Kim said the North should not "even dream of having nuclear weapons", which he said would be a dangerous development. "If North Korea gets nuclear weapons, the stance of Japan and our country towards nuclear weapons would change," he said.

With its highly developed nuclear industry, including plants that could make bomb-grade fissile material, Japan was rated, even as far back as the 1970s Ranger Royal Commission in Australia, as capable of building a bomb within weeks of a decision to do so. In the early 1980s, the US headed off incipient nuclear weapons programs by South Korea and Taiwan, which both have the industrial capacity to build bombs.

The emerging threat of nuclear arms and ballistic missiles is already causing a shift in Japan's defence posture. On Monday the Japanese Self-Defence Agency was reported to be seeking 20 billion yen ($A280 million) to test an anti-ballistic missile system being developed with the US.

Tests could start in Hawaii in April next year.

Last week Japanese Defence Minister Shigeru Ishiba said Japan could launch a military strike on North Korea if there was evidence that it was preparing to attack with ballistic missiles.


I doubt Taiwan would go nuclear, although they probably could within weeks. The United States will not support them if they declare independance. I think we might make a similar threat about nuclear weapons, but, if everybody else suddenly got them, I don't know. Also, if Japan started to increase their focus on personal defence, they might also choose to decrease our military presence there (but maybe not).

Iran restarted their nuclear program a few days ago.

-Biscuits