New Details Emerge About Japan’s Wartime A-Bomb Program


When a captured Nazi U-boat arrived at Portsmouth, N.H., toward the end of World War II, the American public was never told the significance of what was on board.

The German submarine was carrying 1,200 pounds of uranium oxide, ingredients for an atomic bomb, bound for Japan. Two Japanese officers on board were allowed to commit suicide.

Two months later, in the New Mexico desert, the United States detonated the first atomic bomb, a prelude to the obliteration of two Japanese cities.


Unknown to many of the people who built those bombs, not to mention the public, Japan was scrambling to build its own nuclear weapon.

Some of the evidence was the uranium aboard the U-boat that surrendered in the North Atlantic on May 19, 1945, shortly after Adolf Hitler committed suicide on April 30.

Documents now declassified, including the sub’s manifest, show there were 560 kilograms of uranium oxide in 10 cases destined for the Japanese army and two Japanese officers were aboard, accompanying the cargo.

“Germany was collapsing. They had a lot of good uranium. Somebody got this crazy idea of taking it to Japan,” says physicist Herbert York, director emeritus of the University of California’s Institute on Global Conflict and Cooperation.

“The Japanese officers insisted on being given the right to commit suicide.”

German television, Zeit-TV, has aired interviews with crewmen recalling the Japanese officers who killed themselves and were buried at sea.

The uranium oxide is believed to have gone to Oak Ridge, Tenn., bolstering supplies for the Manhattan Project, the U.S. bomb program.

It was even possible--but not probable--that some of the uranium headed for Japan reached there aboard the Enola Gay, the B-29 that dropped the atomic bomb on Hiroshima on Aug. 6, 1945, says U.S. Energy Department archivist Skip Gosling. But the bomb dropped on Nagasaki on Aug. 9 used plutonium, not uranium.

The fact that Japan had been struggling to produce a bomb has been known for decades. How far Japan got remains unclear.

It’s also unclear whether President Harry S. Truman knew about Japan’s program when he ordered the bomb dropped on Japan. Several of the Manhattan Project scientists said in interviews they knew nothing of Japan’s A-bomb program until after the war.

“I don’t think anybody knew,” York said in San Diego. “We didn’t think the Japanese were doing anything. We were worried about the Germans.”

Would knowledge of Japan’s own nuclear program have changed the minds of people critical of Truman’s decision to drop the bomb?

“I think if there were clear evidence of this, it would indeed help to mollify in some way some of the people who are coming out with criticism of our government in using the bomb,” says Steve Stoddard, an engineer who worked 30 years at Los Alamos.

Greg Mello of the anti-nuclear Los Alamos Study Group counters: “It’s incredibly irrelevant.”

The bomb dropped on Hiroshima left almost 130,000 people dead or wounded and leveled 90% of the city. The Nagasaki bomb left about 75,000 casualties.

Military leaders at the time estimated that an invasion of Japan would cost 2 million lives.

Mello contends Japan’s atomic bomb efforts were never a threat. But Robert Wilcox, author of “Japan’s Secret War” (Marlowe & Co.), a book about Japan’s bomb project, says documentary evidence suggests Japan may have gotten further on the bomb than did Germany.

“I know the Japanese were trying to make a bomb all through the war and would have done so had we not ended the war,” Wilcox said by phone from his Los Angeles home. “I have documents showing one of the ways they were going to use it was to put it in kamikaze bombers and send it against the invasion fleets.”

After Japan surrendered on Aug. 15, 1945, the occupying U.S. Army found five Japanese cyclotrons, which could separate fissionable material from uranium. The Americans smashed the cyclotrons and dumped them in Tokyo Harbor.

Wilcox, who updated his book in 1995 with newly declassified material, says the Japanese additionally built six large separators.

Most historians and scientists, including York, say Japan never came close to producing an A-bomb.

“We had hundreds and hundreds of separators,” says John Hopkins, a retired Los Alamos scientist. “We used silver bars out of Ft. Knox to make the low-resistance coils and made hundreds of these mass separators in lines in big banks in buildings. Those were run day and night to separate U-235 from natural uranium. This was separated one atom at a time.”

For all that, he says, America produced only four bombs’ worth of U-235, a fissionable uranium isotope.

“So I would be very surprised if the Japanese had enough uranium,” says Hopkins, who joined Los Alamos National Laboratory in 1960 and was associate director for nuclear weapons. He’s now a member of the Los Alamos Education Group, established to counter nuclear misconceptions.

“To suggest the Japanese were ‘close’ to a nuclear capability is nonsense,” he says.

But there was a program, Hopkins acknowledges.

By most accounts, Japan’s wartime A-bomb efforts were headed by Yoshio Nishina, who had earlier worked in Copenhagen with atomic pioneer Niels Bohr.

The diary of Masa Takeuchi, a worker assigned to Nishina’s thermal diffusion separation project, says Nishina wanted to process hundreds of tons of uranium at the rate of 300 mg per day, according to the U.S. journal Science.

According to Japanese science historian Tetsu Hiroshige, preliminary research for a Japanese bomb program began in 1940, and the program called F-Go, or Number F (for fission), began at Kyoto in 1942.

However, a memoir by Kyoto physicist Bunsabe Arakatsu says the military commitment wasn’t backed up with resources, and the 1978 Science article concluded the danger of a Japanese atomic bomb “was not a real one.”

Wilcox says documents suggest Japan’s military took over the program late in the war with help from Japanese industry and built the separators. He says Japan searched for uranium, buying $25 million worth in China.

Wilcox and Washington, D.C., researcher Charles W. Stone have documents suggesting Japan might have moved its nuclear operation to Korea after U.S. B-29 raids dropped conventional bombs on Japan.

Postwar documents show U.S. concern about a Japanese plant in Hungnam, now part of North Korea, which was captured by Soviet troops at war’s end.

“Consistent rumors from the Hungnam area have dealt with the possibility of atomic research being conducted there,” says a U.S. Army 24th Corps document.

It says the mysterious output of the Hungnam plant was collected every other month by Soviet submarines.

The document seems to partly corroborate an Oct. 3, 1946, report by the Atlanta Constitution, describing a plant in Konan, the Japanese name for Hungnam.

The Constitution writer, David Snell, reported he was a 24th Corps investigator when he learned of the Hungnam plant from a Japanese officer.

Snell said the officer, whom he wouldn’t identify, claimed Japan detonated a small atomic device Aug. 12 on an island off Hungnam three days before Japan’s surrender.

He said the Japanese destroyed the plant, including incomplete bombs, hours before the Soviets arrived.

Immediately after Snell’s article, U.S. investigators began re-interviewing Japanese sources about Hungnam, documents show. At least two sources said that plant had nothing to do with atomic research, interrogation reports say.

Snell said his source told him the Japanese moved their atomic operations there because of the B-29 bomber raids.

“We lost three months in the transfer,” Snell quoted him as saying. “We would have had [the bomb] three months earlier if it had not been for the B-29.”

Akira Yamada, a leading World War II historian who teaches at Tokyo’s Meiji University, told the AP he doubts there was a Japanese atomic bomb program at Hungnam.

Yamada says he has seen no documentary evidence of it, nobody associated with any atomic research there has ever come forward, and no wartime leader ever mentioned atomic research at Hungnam, although other secret research--chemical and biological weapons--came to light.

But it is clear that Japan’s nuclear efforts were interrupted in April 1945 when a B-29 raid damaged Nishina’s thermal diffusion separation apparatus.

After the Hiroshima bombing four months later, the Science report said Nishina was summoned by Japanese commanders who asked about the A-bomb--and “whether Japan could have one in six months.”

But it was just a few days after the Nagasaki bombing that Japan surrendered.

While many people around the world were horrified by the bombings, many were overjoyed. An unidentified man from West Australia, writing in a guest book at the science museum at the Los Alamos National Laboratory, had this to say:

“My mother, sister and I were in a POW camp in Java [Jakarta] when the first bomb went off. As a reprisal, the Japanese were going to place all the camp residents in barges and sink them in the Java Sea. The second bomb saved our lives--and all those innocent women and children held in POW camps all over Java and Sumatra and no doubt elsewhere.

“I am grateful.”