Did Japan test a nuke?

I’m telling the tale of nuclear energy, not nuclear war, but in writing up the early history of power reactors, the German and Japanese stories need to (in my opinion) briefly refer to their World War II nuclear experiences vis a vis the successful Manhattan Project. In other words, when it came time for the Japanese and Germans to consider nuclear electricity, what was their background, their atomic expertise?

Research data

There is plenty of material on Germany’s wartime A-bomb efforts, much less stuff on the Japanese attempts. When I assembled my research data on this topic back in 2008 (yes, I know it’s a long time ago), I stumbled across Japan’s Secret War: Japan’s Race Against Time to Build Its Own Atomic Bomb, a 1985 book by Robert Wilcox, an American journalist. Intrigued, I figured out that none of my close-by research libraries stocked it, so I bought a second-hand copy (as pictured here) that once belonged to The Public Library of the District of Columbia. In 2015, I did an analysis pass on early Japanese nuclear history. Japan’s Secret War claims, at its most sensationalistic, that Japan successfully tested a nuke, in a secret North Korean cave complex (called Hungnam) just days before the nation’s August 1945 surrender. I scribbled in my notes: “outrageous!”

Now, writing up Japan’s 1945-1960 nuclear power history, I find myself confronting Japan’s Secret War again. Astonishingly, just three months ago, Wilcox published a third edition; the blurb describes it as “revised and greatly updated.” Based on my analysis, I expected to not even make mention of the book’s thesis (or maybe to give it a glance in a footnote). Shallow Googling pops up favorable reviews echoing the book’s radical claims. Do I need to buy this book, to wait for it to wend its way to my Coronavirus-locked-down doors (it’s not in ebook form)? Do I need to restudy it?

So I dig deeper and indeed don’t need to excavate much more. A 1986 review of the original 1985 edition of Japan’s Secret War was penned by John Dower, an eminent historian on wartime and post-war Japan, Judith Preppy, and the doyen of historians concerning the Soviet Union’s nuclear history, David Holloway. Their review rips Japan’s Secret War to shreds (while crediting the book with some useful insights). Here’s one judgment:

This is rumor reiterated, not confirmed; and, indeed, Japan’s Secret War offers not a single piece of hard, credible evidence that serious atomic energy research was conducted in Hungnam, let alone that the Japanese actually tested an atomic weapon successfully.

So I’m happy with my original assessment.


Wilcox, Robert K. 1985. Japan’s Secret War: Japan’s Race Against Time to Build Its Own Atomic Bomb. William Morris and Company, New York.

Dower, John W., Judith Reppy & David Holloway. 1986. “Reviews.” Bulletin of the Atomic Scientists, 42, Sep., pp. 61-64.