THE hand-wringing over the nuclear destruction of two Japanese cities that occurs every August is fully understandable. The anniversary reports, however, seldom mention that the Germans and the Japanese were in the race to build the A-bomb.

If the war had started later or lasted a little longer, nuclear history might well have read differently.

On Aug 5, 1945, Professor Yoshitaka Mimura of Hiroshima Bunri University was explaining to a seminar for officers in the Japanese army's Hiroshima garrison how nuclear fission might be applied to warfare.

'A nuclear bomb could be even smaller than a piece of caramel candy,' he told them, 'but if it exploded at 200m above a populated city, it could destroy 200,000 lives.'

A colonel had a question: 'When can we have that bomb?'

The professor's response: 'It's difficult to say, but I can tell you this much: not before the end of this war.'

Some 20 hours later, the professor was standing on a neighbour's porch chatting to an acquaintance when a massive shock wave lifted Mimura-san off the floor and hurled him inside the house.

It was 8.15am, Aug 6. Although Japanese army and navy scientists, in separate research projects, were on the trail of nuclear fission, they had been unable to get their act together in sufficient time to please the colonel. The enemy had beaten the Japanese to that awesome rendezvous.

The Germans' effort depended on plants in occupied Norway that manufactured the heavy water (deuterium oxide) important in producing a sustained nuclear chain reaction. Four determined assaults by Norwegian and British soldiers and American airmen between 1942 and 1944 destroyed these facilities.

In the apparent hope that their Japanese ally could carry the work further, the Germans sent a submarine with a cargo containing 560kg of uranium oxide from Kiel towards Japan in March 1945. The oxide contained some 3.5kg of the isotope U-235, about a fifth of the total needed to make one bomb.

When word came of Chancellor Adolph Hitler's death late in April, the sub surrendered to US forces in the north Atlantic. According to some recent accounts, the Americans may have used the sub's uranium in the manufacture of the first three A-bombs.

One American investigator, Robert Wilcox - author of Japan's Secret War: Japan's Race Against Time To Build Its Own Atomic Bomb (Marlowe & Co, New York, 1995) - contends that Japan tested a nuclear device successfully on Aug 12, 1945, at Hungnam, then part of the Japanese empire and now in North Korea. He quoted from an archived transcript of an interview with a Japanese counter-intelligence agent.

In a book published this June - Secret Weapons And World War II: Japan In The Shadow Of Big Science (University Press of Kansas) - historian Walter Grunden questions this claim. He says that though there may have been an explosion that day, he does not think it was nuclear.