The world's first operational atomic bomb was dropped above the Japanese city of Hiroshima at 8:15 on the morning of the 6th of August 1945. It was carried to its target by the USAA B-29 bomber Enola Gay, flying from the American airbase on the Pacific island of Tinian. Nicknamed 'Little Boy', the bomb exploded with the equivalent force of over 12 kilotons of TNT. Around 5 square miles of the city was reduced to ashes with over 60% of the total building stock destroyed. Within four days of the blast, some 120,000 civilian inhabitants had died many of them having been instantly vaporized by the explosion. Three days later at around 11a.m on the 9th of August, another B-29 bomber from the Tinian airbase dropped the second operational atomic bomb on the city of Nagasaki.
This one was nicknamed 'Fat man' and had a similar impact to the Hiroshima bomb - approximately 2.5 square miles of the city were laid waste and over 70,000 people were killed as an immediate result of the blast. What had led to the fateful decision to deploy these new weapons of mass destruction?
Stephen Walton: "So, the war in Europe had ended in May 1945 with the death of Adolf Hitler in the Berlin bunker and the subsequent unconditional surrender of Germany and her remaining European Allies. This had been made possible by the Normandy landings of June 1944 and the ensuing campaign to push German forces back to the Rhine and beyond. Combined with the unstoppable advance of the Red Army on the eastern front, this effectively crushed the German forces between two gigantic Allied steamrollers."
But the war in the far east against Japan continued. Considerable American, British and Commonwealth land, naval and air forces were committed to a war of attrition over a vast area. Japanese forces fought with fanaticism and with little regard for casualties on either side. Before the advent of the atomic bomb in July 1945, the US and her Allies were planning for a conventional military defeat of Japan as they had done previously for Germany with Operation Overlord. The equivalent plan for the Far East was called Operation Downfall.
Stephen Walton: "Downfall was designed to overrun the Japanese home islands and bring about the desired unconditional surrender. Planners envisaged that their forces would not be ready to begin the operation until November 1945 and they were expecting the whole campaign to last well into the spring of 1946."
Had it taken place, Downfall would have been the largest military operation of its kind in history, putting even Overlord into the shade. But likely American and Allied casualties were a major concern for the planners and the American government.
Stephen Walton: "It was assumed that downfall would inevitably cost the invaders very dearly in this regard. Estimates vary widely, worst-case scenarios predicting several million American casualties in dead and wounded."
Another key concern was the possible impact on the substantial allied prisoner of war population in Japanese hands. Some 100,000 Allied personnel were in POW camps towards the end of the war and it was feared that in the event of an invasion they would all be massacred by their captors. Orders issued previously to POW camp commanders seemed to suggest that in the event of an invasion they would be killed to prevent any possible uprisings.
Stephen Walton: "A smaller scale preview of what Downfall might look like was provided by the Battle for Okinawa during April to June 1945.
Just over 300 miles from the Japanese mainland, this large island was a vital staging pose for any invasion force, particularly as a forward air base. The Japanese defence was mainly concentrated inland away from the immediate invasion areas, but the Americans were immediately hit by massed kamikaze attacks which inflicted heavy casualties amongst the naval forces, and that was even before the marines and infantry came up against the strongly defended Japanese positions further inland."
The projected cost of Operation Downfall, particularly in terms of allied casualties as well as the experience of the bloody and bitter fighting for Okinawa, combined to increase the desire for an alternative war-winning strategy.
Stephen Walton: "So, with what seemed like providential timing, the successful testing of the world's first atomic bomb in the desert of New Mexico on the 16th July1945 offered just such a solution. This had been the result of several years of American-led research and development codenamed the Manhattan Project, partly motivated by the need to respond to Nazi Germany's own wartime atomic bomb project, although this was later known to have been much less further developed than the Americans had assumed."
From the outset Japan had also been a potential target for this new type of bomb and the Allied leaders now had little hesitation in acting accordingly. The declaration they issued at the conclusion of the Potsdam Conference threatened Japan with 'prompt and utter destruction' if she did not accept unconditional surrender. Her military hardliners blocked any moves in this direction and the decision to deploy the Atomic bomb was made.
Stephen Walton: "Hiroshima was selected as the first target as it was an important economic and military hub that had so far escaped serious air raid damage. When the Japanese surrender was still not forthcoming, Nagasaki became the second target.
Even after this second demonstration of catastrophic destructive power, it took almost another week for the Japanese government to finally accept defeat and this only as a result of an unprecedented intervention by the Emperor Hirohito who forced his hardliners to bow to the inevitable."
So, the Second World War was ended with no further allied military losses on the battlefield but at a terrible cost to the Japanese civilian population, and with it the spectre of Mutually Assured Destruction that dominated the Cold War era.
Hiroshima and Nagasaki were essentially experiments in a new kind of warfare whose full implications were not entirely understood at the time. Were the Allies justified in using the atomic bombs to bring an end to the war? Should they have stuck to the conventional plan as envisaged by Operation Downfall? Were there any other potential alternatives?
Let us know what you think in the comments below.
Stephen Walton: "Hello again, if you've enjoyed this video and would like to see more in the series then please do log on to the IWM's YouTube channel and like and subscribe there. Thank you."
