This article is part of Engelsberg Ideas’ latest series, ‘The Nuclear World Transformed’, in which our writers explore the history and current state of the global nuclear landscape, and how it is being reshaped by a new age of great-power competition. 

American military technology leapt forward as a consequence of the United States’ entry into the Second World War after the attack on Pearl Harbor in December 1941. On land, sea and in the air, the country’s industrial might was focused on expanding its military infrastructure at home, ramping up enlistment across all arms of its services, and producing the weapons and equipment that would make it possible to fight a war on multiple fronts. The key aim would be that superior machines, not humans, would bear the brunt of destroying their enemies.

One important aspect of this would be in the air, to deliver a killer blow to both Imperial Japan and Nazi Germany. American ingenuity in aviation and ordnance would produce a variety of four-engine, long-range bombers, and the deadly payloads of incendiary and high-explosive cannisters they would carry, with one stated aim: to reduce Japan and Germany to rubble and ashes. The arrival into the war of the futuristic B-29 Superfortress would fulfil the stated aim of forcing unconditional surrender on Japan with whatever weapon could achieve that.

In both the European and Pacific theatres, ‘Total War’ targeted those civilian populations deemed to be on the frontline. But whereas cities might be destroyed through traditional means of both artillery and aerial strikes, these could take days, weeks, and months of fierce urban combat. Nanking in Eastern China, Stalingrad in southern Russia, and Manila in the Philippines – all witnessed bloody military campaigns that drew in civilian populations, and inflicted hundreds of thousands of casualties. Though in many cases, these deaths would be chalked up as an ‘atrocity’, one might argue this was achieved through traditional, or ‘acceptable’ methods – whether by bomb, shell, bullet, or bayonet.

Arguably the greatest, mass-produced weapon of the Second World War, at a cost to the American taxpayer of over $4 billion, the B-29 pushed the frontiers of design, engineering, and technology in rapid time. It would be the vehicle from which the United States would conduct the indiscriminate firebombing of the Japanese population in 1945. The dividend to American military planners of employing an aircraft that was almost untouchable in the air would be huge and, on the flipside, prove apocalyptic for the Japanese. American air raids across the Japanese Home Islands throughout 1945 would reduce 66 cities to smouldering ashes, killing over 900,000 civilians and de-housing another 8.5 million.

Yet, despite this wholesale destruction, the Japanese leadership would only finally submit once a more destructive force was unleashed. A secret weapons programme, later titled the Manhattan Project, which brought together the finest scientists of the free world, working alongside the power of American military and industry, to create and build the world’s first nuclear weapons. The two atomic bombs – the uranium-made ‘Little Boy’ and the plutonium-filled ‘Fat Man’ – dropped on Hiroshima and Nagasaki respectively, brought a brutal conflict to a sudden end on 15 August 1945. President Harry S. Truman’s announcement caught most Americans by surprise; they believed the fighting would last considerably longer and cost significantly more losses.

The atomic attack on Hiroshima by the lone B-29 bomber flown by Colonel Paul Tibbets Jr, in the Enola Gay, marked the culmination of a new and terrifying way of humanity waging war within the prewar agreements drawn up in the Geneva Convention.

In a split second, Little Boy detonated the equivalent of 15,000 tons of TNT. The temperature close to the epicentre of ground zero reached several thousand degrees centigrade, as hot as the surface of the sun. Anything flammable burst into flame, the explosion causing an enormous firestorm, consuming everything within a mile radius. Within minutes of the blast, nine out of ten people caught half a mile or less from ground zero were dead; approximately 80,000 people perished, the figure rising past 120,000 in the following weeks as survivors died from a new condition – radiation sickness.

The bombing of Nagasaki three days later unleashed yet more terror and suffering, killing 40,000 initially; by year’s end the figure rose past 70,000. Their successful use in August 1945 would forever change how future powers strategised warfare. If such a weapon should proliferate around the globe, they could not just destroy cities, but would wipe out civilisation itself. They would change the postwar world forever.

The Japanese empire’s acceptance of unconditional surrender was a unique moment in history. Despite having close to two-and-a-half million troops in readiness, a civilian population of millions conditioned to fight to the death, and thousands of Kamikaze naval and air units prepared to inflict maximum casualties on an American invasion, they chose to surrender. It was the only time in modern history that a major industrial nation chose to do this without a single enemy soldier occupying its territory. On 2 September, a formal signing of surrender was conducted aboard the US naval battleship USS Missouri in Tokyo Bay.

A 1943 poll commissioned by senior US Army leaders had shown that 50 per cent of all GIs believed it necessary to kill all Japanese before peace could be achieved. With the bombs dropped, and the war ended, on 30 November 1945 a Fortune Survey found that 17 per cent of those Americans polled thought the bomb shortened the war by two to five months; 35.6 per cent said from six months to a year; and 17.6 per cent declared without the bomb the war would have lasted over a year. The poll further indicated that 8.4 per cent believed the bomb did not shorten the war at all, while 9.9 per cent said it shortened the war by one month or less. A carefully managed PR campaign after war’s end by the Manhattan Project fended off any suspicion of the dangers that might be associated with this awesome new power given to the American military. It would take another year before credible voices, such as John Hersey’s article in the New Yorker, began to be heard, finally showcasing the poisonous and deadly legacy that an atomic bomb could inflict upon humanity.

The Manhattan Project would be re-designated on 31 December 1946. It had cost approximately $500 million to make each of the four bombs. Under President Truman, the old alliance with the Soviet Union would disintegrate. Joseph Stalin’s Red Army of over five million troops remained in central Europe, suppressing democratic groups, and supporting puppet regimes in the satellite states of Czechoslovakia, Bulgaria, Poland, Romania and eventually East Germany. To combat this threat, Truman’s administration would direct the economic might of the United States into the ‘Marshall Plan’, the reconstruction of war-torn Europe.

His government’s policy of tackling head-on any communist insurgency around the globe was known as the ‘Truman Doctrine’. It would kick-start an arms race with the Soviet Union, with nuclear technology at its heart. As J. Robert Oppenheimer and his mentor, the great Danish physicist, Niels Bohr, had predicted – it was now a nuclear race. What they had not foreseen was how far Soviet spies had penetrated US military security at Los Alamos, to reveal the Manhattan Project’s atomic technology and create their own nuclear programme in record time. It would usher in the Cold War and the paranoia of the McCarthy witch-hunts.

Truman never regretted using the two atomic bombs to end the war. He had a weapon, the enemy did not. Using it would tip the scales in the United States’ favour. He wanted the war to end and prevent more Americans losing their lives needlessly when the enemy was clearly on its knees. So, he ordered its use. As the author Leslie Blume concludes in her book, Fallout: ‘Throughout the remaining years of his presidency, Truman would always keep atomic weapons in “active consideration” for use in military situations that might arise on his watch. They were no different, he stated, from conventional weapons, just bigger, more efficient, and more effective – a legitimate part of the US arsenal. His successor Dwight D. Eisenhower felt the same.’

For humanity, the age of MAD (‘Mutually Assured Destruction) had arrived. We are still living with its threat today.