¿Why Japan is wary of North Korea's Musudan missiles?

North Korea has recently claimed a series of breakthroughs in its push to build a long-range nuclear missile that can strike the American mainland. If the North's claims about the sixth Musudan launch are true, it would pose a threat to the USA military base in Guam, where troops that would be sent to the Korean Peninsula if conflict broke out are based, and also possibly a nuclear threat. It explains in part North Korea's tenacious testing of the Musudan missile. (Read more)