Obama's Asian nuclear nightmare

President Barack Obama's trip to Asia next week will be anchored by a stop in Hiroshima, where he will focus on its dark nuclear past.

But Obama’s visit comes at a moment when U.S. and Asian officials fear the region is entering a newly dangerous atomic future, threatening Obama’s vow to roll back the spread of nuclear arms and possibly touching off an Asian nuclear arms race.

North Korea is expanding its nuclear arsenal and upgrading its ballistic missiles. China is growing and modernizing its stockpile. Most strikingly, Pentagon planners worry that Japan and South Korea might for the first time explore developing nuclear arms of their own — promoted in part by the recent conclusion by U.S. and South Korean intelligence agencies that North Korea’s bizarre regime can now mount a small nuclear warhead on missiles capable of striking Japan and South Korea.