LOS ALAMOS, N.M. — 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.