The election of Donald Trump as U.S. president threw a potential bombshell into diplomatic, political and military relations all over the globe. His subsequent unpredictable interventions have raised the basic question in every capital in the world: Can we trust this guy?

This is especially so for Japan, for which the U.S. alliance has been the foundation of its security and diplomatic policy since the war. Trump's mercurial unpredictability raises the hitherto unthinkable question — if Japan cannot rely on Trump's U.S., should it develop its own nuclear weapons?

The president-elect's lack of foreign policy experience, except as business deal-maker building his eponymous empire, is one concern; more worrying is his tendency to shoot his mouth off with a rambling instant opinion, and then later to deny he said it.