Today is VJ Day, the 73rd anniversary of Japan’s surrender in 1945. Perhaps understandably, the war against Japan has been overshadowed in our memories by the war against Germany. Japanese militarism never represented the same existential threat to us as Nazism. But we shouldn’t let the sacrifices and heroism, or the scale, of those dreadful events slip from our minds. From China to the mid-Pacific, millions died and tens of millions endured appalling hardship. And while we remember those events, as with all history, we should be on our guard about how they are portrayed today.

This is especially true of the war’s ending and America’s use of atomic bombs; something that has been deeply contentious ever since 1945. We should be grateful our society can ask hard questions about using such terrible weapons yet we should be wary of how those events might be woven into contemporary politics.

The Campaign for Nuclear Disarmament’s website tells us that America’s use of atom bombs on Hiroshima and Nagasaki was unnecessary. Its general secretary Dr Kate Hudson argues that when the bombs were dropped, Japan was ready to surrender. America simply wanted to demonstrate that it would not allow Soviet domination of Japan and the Far East after the war.

Some might point out here that CND is an organisation that has often been loudly cheered on by the Soviet Union, with its own nukes and long history of aggressions; but we should avoid ad hominem attacks. There is no reason to doubt Dr Hudson’s good faith. She cites Dwight Eisenhower, who argued after the war that the bombings had not been needed. Given his role as supreme commander in the Allied invasion of Europe and later presidency, his is a voice that clearly carries significant weight.

Japan’s position in 1945 was certainly hopeless, but much of its leadership were either in deep denial or barely cared, happy to accept some awful Wagnerian fate for their nation. The atom bombs were the unarguable shock to show Japan it had lost. There could be no equivocation and a speedy surrender meant a speedy end to the dying.

Really, Japan lost the war at its very beginning, but it didn’t realise. It had gambled on knocking out America and the Allies in a series of lightning blows. When these failed and America had time to bring its huge strength to bear, victory became impossible. Japan had roughly half of America’s population, a fraction of its industry, lacked crucial raw materials and was already locked in a terrible war in China.

Japan’s strategy against America demanded naval supremacy and the destruction of US aircraft carriers – the super-weapon of the day. Its attempt to achieve this with the surprise attack on Pearl Harbor failed. America’s carriers were out at sea. The main target was missed, but America was enraged.

In the next few months, Japan achieved some impressive results but no knock-outs. Then came disaster: between May and June 1942, Japan lost half its aircraft carriers in two battles, the Coral Sea and Midway, and with them the ability to block the massive and growing power of America coming across the Pacific. Daring and ruthlessness would not be enough against America’s factories, shipyards, refineries and steel mills.

America’s production of ships, planes, guns, trucks and every conceivable article of war material is one of history’s greatest achievements. In 1942 alone, America built 125,000 military aeroplanes. Between 1942 and 1945 it launched 17 aircraft carriers, not counting 71 smaller escort carriers, to Japan’s six. By 1945, America produced half the world’s industrial output. Although much was prioritised for fighting Hitler, Japan’s strength was equally divided on other fronts such as the continued resistance in China or the ‘forgotten’ war against British and other allied forces in Burma.

But even as chances of victory, or of at least fighting the Americans to a standstill, disappeared, nothing weakened Japan’s ferocious resistance rooted in militarism, nationalism, medieval emperor worship and nihilism.

By late 1943, even Emperor Hirohito declared the situation ‘truly grave’. Allied air and naval superiority became complete domination, cutting off much of Japan’s widely dispersed forces from supply and support. The home islands were blockaded and increasingly subject to massive air attacks as the Americans established ever-closer bases for their bomber fleets.

Little could dent Japanese resolve though. Death for the emperor was glorious; surrender the ultimate disgrace. Even civilians fell for this madness. Battles on Saipan in 1944 and Okinawa in early 1945 saw mothers clutching children hurl themselves from cliffs and the elderly blowing themselves up with grenades rather than fall into American hands. America feared that in any invasion of Japan’s mainland that spirit would mean savage fighting for every yard of territory, and an astronomical cost in blood.

The revisionist view is that these fears have been seriously overstated and the Japanese were busily looking for a way out that would leave them with at least some honour. There are two problems with this argument. First, although there was a ‘moderate’ party within the Japanese military and government, there was an equally strong or stronger bloc of hardliners. There is no reason to suppose that without the atomic bombings, the moderates would have gained dominance.

Then there is time – every single day brought death at an alarming rate. Millions were already dead from battle, deliberate extermination, starvation and disease. Famine had already struck in Vietnam, China and Indonesia and the prospect of further mass starvation was hideously real. Deliberate Japanese atrocities against civilian populations, war prisoners and internees were constant, their army at times truly barbaric. Every month of continued war would have a hideous cost.

We can never know exactly how events would have played out had Truman not used the bomb. We cannot be certain he made the correct choice and we should not forget or downplay the awful tragedy of the bombs. But we can make a grim utilitarian calculation and be reasonably sure that those bombs saved more lives than would have been lost had the war continued for anything more than the very shortest of periods. That is the only consolation we can take.