The accepted explanation for why the administration of President Harry Truman dropped the bombs was that it brought a swift end to the Pacific war and thus saved many more lives than those lost at Hiroshima and Nagasaki. This first and only use of atomic weapons was, it has been claimed, a classic case of the end justifying the means.
But what if this "end" is shown to be false, and that the real reason for the atomic holocaust was not the swift termination of hostilities but an entirely different purpose, namely the staking out of Western geopolitical territory in the emerging post-war world order?
From April 1945 American officials calculated that using the atomic bomb would enormously bolster US diplomacy vis-a-vis the Soviet Union in negotiations over both post-war Europe and the Far East. The ascendancy of "atomic diplomacy" coincided with the presidential succession of the fiercely anti-Communist Truman.
A defining moment of the new diplomacy occurred during the Potsdam conference on 13 July when Truman was cabled from Washington on the success of the "Trinity" test explosion in the New Mexico desert. It was the first practical demonstration of awesome atomic power.
The news transformed Truman's diplomacy at Potsdam. He immediately began dominating the proceedings, telling the Russians "where to get on and off". Possession of the bomb gave Truman the "master card" over the Soviets, recorded the US war secretary Henry Stimson.
The Soviets planned to enter the Pacific war against Japan on 9 August; the Western allies were anxious they should not gain any geopolitical territory in resource-rich Asia, as they had done in Europe.
During the summer of 1945 when the Japanese empire began rapidly to collapse, the first concern of Truman and his inner circle was not the further loss of American lives, but the further loss of political ground in the new world order taking shape.
Japan may have been the military target of the US atomic attack first on Hiroshima on 6 August, and then three days later on Nagasaki, but there seems little doubt from the evidence that the ultimate political target was Moscow.
On hearing of the annihilation of two Japanese cities in which 95 per cent of the victims were civilian, Josef Stalin was said to have been "frozen". The Soviets had no nuclear weapon project and may not even have had the rudiments of the theory.
The bombing of Hiroshima and Nagasaki turned out to be not the last act of the Second World War but the first act of the Cold War. It was a deliberate act of aggression by the US, designed to lay down the most terrifying marker on the new world order to the Soviets.
By 1948, however, the Soviet Union had tested its first atomic bomb. Fear and distrust in international relations had become entrenched and the world was now forced to live under the shadow of mutually assured destruction.
The fall-out from the atomic attack on Hiroshima and Nagasaki was inestimably far-reaching; all malignant manifestations of the nuclear age can be traced to that fateful decision to drop the bombs.
It is important to lay bare the bankrupt moral authority of great power status. It provides an important step towards getting rid of all nuclear weapons - by uncovering the real causes of history, we may be spared its horrendous repetition.
`Hiroshima's Shadow - writings on the denial of history' is published by Central Books (pounds 20.90)