This version of history has become the received wisdom for two reasons. We know everything that is to be known about the horror of those first aggressive nuclear explosions. No events in the Pacific War - nothing else in the whole course of the Second World War except perhaps the Holocaust - has received such exhaustive attention. We have in a sense lived in their shadow ever since. If ever in history man has executed terminal acts, taken on the mantle of the gods and hurled thunderbolts, those days in August 50 years ago were the time. Somehow we need to believe that the consequences were correspondingly epic.
The second reason is that, although the decision to drop the bombs was taken swiftly and without much apparent heart-searching, their effects were so ghastly that their use has excited furious argument ever since. At the most extreme it has led to hysterical comparisons between Hiroshima and Auschwitz. America, longing to believe that in both Europe and the Pacific it was fighting "the good war", in the final act suddenly found itself recast as principal monster. The only way to rebut such charges was to claim overwhelming necessity - and efficacy. The bombs were dropped. Within eight days Japan surrendered. Therefore the bombs ended the war. Thereby half a million American lives and millions of Japanese lives were saved. The Bomb was horrible, but it was worth it.
Nevertheless, the argument has never been clinched. It is a scab that American historians and journalists cannot resist picking, a game they have continually to replay in their heads, to make sure they come out morally on top. As the blurb of a new book on the end of the war puts it: "What would have happened if the atomic bombs had not been dropped on Hiroshima and Nagasaki, and the Allies had had to invade Japan to end the war?"
That is a very sly begging of the question. Because the reason there is any dispute about what caused Japan to surrender is that, between the dropping of the two bombs, another momentous event occurred.
Hiroshima was bombed on 6 August, Nagasaki on the 9th. But on 8 August the Soviet Union, neutral until then, informed Japan that it was declaring war; the next day it invaded Manchuria, China and Korea. Given that none of these developments was welcome, which was it that persuaded Japan to sue for peace?
The destruction of Hiroshima undoubtedly shocked the Japanese authorities. They quickly learnt from Yoshio Nishina, the physicist in charge of Japan's own rather pathetic version of the Manhattan Project, that an atomic device was probably to blame. The Japanese knew how hard it was to obtain the uranium necessary to build a bomb - after two years of trying, Japan's scientists had managed to produce only a wafer of uranium about the size of a postage stamp - and Admiral Toyoda, chief of staff of the imperial navy, believed that the Hiroshima bomb was the only one America possessed. But a rumour swept through Japanese official circles after Hiroshima, based on the imaginative testimony of a downed American pilot, that Kyoto and Tokyo would also suffer nuclear attack within the next few days. When Nagasaki was pulverised, the question arose of who was to get it next.
Kyoto, the old imperial capital, had been completely spared until then, thanks to the lobbying of American Japanophiles in Washington. But in the case of Tokyo, there was nothing much left to hit. The raids of 9 to 10 March 1945, which killed more than 100,000 and left a million homeless, were the most destructive of the whole war, including Hiroshima. Yet the B-29s had continued to return to bombard the capital. Although the bombers were explicitly banned from targeting the imperial palace, a firestorm started by a raid on 25 to 26 May destroyed 27 buildings in the palace complex and killed 28 members of the emperor's staff, while Hirohito, the empress and their attendants huddled in their shelter 60 feet below ground.
Bombing, even atomic bombing, is subject to the law of diminishing returns. Kyoto would have been a tragic loss - though it is doubtful whether at that juncture even the Japanese were in a mood to worry about temples and rock gardens. But the Americans were running out of targets. More than 60 cities had already been burnt. Millions of civilians had been evacuated to the countryside, including all but 200,000 of the population of Tokyo. The economy was at a standstill. The infrastructure was in ruins. No work was being done, nothing was being manufactured. The only thing another bomb could do was kill more people.
The theory that Hiroshima and Nagasaki ended the war rests on the assumption that the Japanese authorities were concerned about the fate of ordinary Japanese people. But if this had been the case, the war would not have been prosecuted in the way it was. After the bombing of Pearl Harbour in December 1941, for example, the Japanese forces stampeded through South- East Asia and the islands of the Pacific, occupying Burma and reaching New Guinea before they were checked. So rapid was their advance that they far outstripped their lines of supply. The result was that, when they encountered Allied resistance, they quickly began to starve. The numerous cases of Japanese soldiers killing and eating Australians, New Guineans and even each other is nothing to do with their bestiality as human beings and everything to do with the bestiality of their supreme commanders in Tokyo.
From early on in the war, Japanese soldiers were called on to make the ultimate sacrifice - to throw away their lives, either through starvation or banzai charges or, later, kamikaze attacks. When, in mid-1944, the war began to reach Japanese civilians, the expectation was the same. In Saipan, where the Japanese soldiers fought practically to the last man, the civilian population, too, was required to die, most commonly through mass suicides over the cliffs. It was the same story 10 months later in Okinawa. By the end of the war Japan resembled not so much an ordinary nation as a vast, apocalyptic cult. Its members' only goal was to die for the emperor.
Yet those at the heart of the nation, the heart of the cult, retained a certain flinty realism not permitted in their subjects. The people might die in a million gallant ways, but the emperor and his line must live. It was with this in mind, as the war situation became increasingly desperate, that the emperor's closest advisers began casting ever more anxious eyes at their mighty neighbour to the West, the Soviet Union.
Russia and Japan's destinies had been intertwined since the dawn of Japan's modern era. As early as 1805 a Russian ship had tried to open Japan to trade; in 1852, when the American Commodore Perry's black ships finally achieved that, Russia's Admiral Putyatin was only just beaten to the punch. As Japan modernised and sprouted imperial ambitions, the two nations clashed over Manchuria and Korea, and in 1904-5 fought a bitter 18-month long war, which Japan won.
In 1938, when the Japanese army, at its most rampant, was stampeding through China, ferocious battles were fought with the Red Army on the Siberian and Mongolian borders, and if the crazier voices in the Japanese army and cabinet had had their way, Japan would have gone to war against Russia soon after Germany did, welching on the Soviet-Japan Neutrality Pact that had been signed in April 1941. At this point, however, some semblance of sanity prevailed, and Japan drew back.
As the war developed "not necessarily to Japan's advantage", in Hirohito's famous phrase, Japan's relationship with the Soviet Union began to assume ever greater significance; its neighbour's neutrality bulked large in the hopes and fears of Japan's rulers. On 5 April 1945 the Soviet Foreign Affairs Commissar, Molotov, informed the Japanese ambassador that once the neutrality pact expired in April 1946, it would not be renewed. Japanese intelligence reported a massive movement of Red Army troops and supplies towards the Manchurian border. A clandestine transmitter began inciting Manchuria's large Russian population to revolt; the Japanese consul general in Harbin told Tokyo that he believed it was part of a campaign to give the Soviets a pretext for invading Manchuria. The Japanese began to worry. (If they had known that Stalin had promised the other Allies he would enter the war against Japan within three months of Germany's defeat, of course, their alarm would have been considerably greater.)
In its desperate attempt to keep Russia sweet, Japan launched a manic diplomatic offensive: offering to give up Manchuria, carve up China, and flood the Soviet Union with raw materials from the lands Japan had conquered (something it was in no position to do). Most bizarrely, on 14 June, the former foreign minister Koki Hirota offered the Soviet ambassador, Jacob Malik, the prospect of a Soviet-Japan alliance in the Pacific. "Japan will increase her naval strength in the future," Hirota told the Russian, "and that, together with the Russian army, would make a force unequalled in the world." A proposal more insanely remote from Japan's actual circumstances is hard to imagine, unless it was to offer to co-operate in a moonshot. Malik, who must have had trouble keeping a straight face, said he would study the proposal.
Unsurprisingly, none of Japan's ideas got anywhere.Finally, Molotov agreed to meet the Japanese ambassador on 8 August. But Molotov's message was the opposite of what the ambassador had been hoping to hear: the Soviet Union was declaring war. The next day Manchuria, China and Korea were invaded, and it might only be days before it was the turn of Japan's home islands. If that happened, there was little reason to doubt Soviet intentions. Soon there would be a red flag flying over the palace of the supreme soviet of the Socialist Republic of Japan, and the emperor and his line would be extinct.
With the Russians at one end of the country and the Americans at the other, it was the devil and the deep blue sea - so the deep blue sea bore closer examination, in case it might be possible to swim in it. Late at night on the day of the Soviet advance, a top-level conference, a so-called gozen kaigi, was held in the presence of the emperor 60 feet under the imperial palace. The chief secretary to the cabinet read the Potsdam Declaration (which had been received 13 days before) aloud. It did not escape notice that whereas previous Allied ultimatums had demanded "unconditional surrender" pure and simple, Potsdam called for "unconditional surrender of all armed forces". It could be a key concession.
To establish whether it was, the Japanese Foreign Ministry cabled the Allied governments that it was ready to accept the declaration, "with the understanding that the said declaration does not compromise ... the prerogatives of His Majesty as a Sovereign Ruler".
"Let them keep the son-of-a-bitch!" American GIs in the Pacific yelled, when they heard of the Japanese demand. Keep him they did.
Hiroshima and Nagasaki will go down in history as two of the most cruel and awesome acts of war of the 20th century, but the defining influence they have since had on political and military history is due partly to the erroneous belief that they abruptly ended the war. Yet compared to the threat of invasion by the Soviet Union, their influence on the decision of the Japanese to surrender was marginal. The menace of the nuclear bomb will always be terrifying; but the notion that it has unique political potency turns out to have been a myth all along.