Monday marked the Hiroshima day, the anniversary of the dropping of the first atomic bomb. As the wartime generation passes on, our sense of gratitude is increasingly mixed with unease regarding one theatre of the second world war. There is a widespread conviction that, at Hiroshima and Nagasaki, America committed acts that were not only terrible but also wrong.

Disarmament campaigners are not slow to advance further charges. Greenpeace maintains that a different American approach might have prevented the cold war, and argues that new research on the Hiroshima decision “should give us pause for thought about the wisdom of current US and UK nuclear weapons developments, strategies, operational policies and deployments”.

This alternative history is devoid of merit. New historical research in fact lends powerful support to the traditionalist interpretation of the decision to drop the bomb. This conclusion may surprise readers of a liberal persuasion. The so-called revisionist interpretation of the bomb made headway from the 1960s to the 1990s. It argued that Hiroshima and Nagasaki were less the concluding acts of the Pacific war than the opening acts of the cold war. Japan was already on the verge of surrender; the decision to drop the bomb was taken to gain diplomatic advantage against the Soviets.

Yet there is no evidence that any US diplomat warned a Soviet counterpart in 1945-46 to watch out because America had the bomb. The decision to drop the bomb was founded on the conviction that a blockade and invasion of Japan would cause massive casualties. Estimates derived from intelligence about Japan’s military deployments projected hundreds of thousands of American casualties.

Truman had to take account of this, and dropped the bomb for the reasons he said at the time. Contrary to popular myth, there is no documentary evidence that his military commanders advised him the bomb was unnecessary for Japan was about to surrender. As the historian Wilson Miscamble puts it, Truman “hoped that the bombs would end the war and secure peace with the fewest American casualties, and so they did.” Sadao Asada, of Doshisha University, Kyoto, has concluded from analysis of Japanese primary sources that the two bombs enabled the “peace party” within Japan’s cabinet to prevail.

One of Japan’s highest wartime officials, Kido Koichi, later testified that in his view the August surrender prevented 20 million Japanese casualties. The destruction of two cities, and the suffering it caused, cannot but temper our view of the Pacific war. Yet we can conclude with a high degree of probability that abjuring the bomb would have caused greater suffering still.

Commemoration of war is part of our civic culture, and campaigners against Trident and the missile defence have every right to state their case. But those things must not be confused. The campaigners must advance independent grounds for their policy views. Dubious historical claims are not the right way to advance them. — The Guardian