Here's my answer to a similar question that was asked a bit back.
It's is important to recognize that at the time the Atomic bomb was not full of the same connotations that we put on it now. Back during the 30's and 40's Atomic Weapons were simply envisioned as bigger bombs and the myriad secondary effects weren't fully understood at the time.
Opinion on the dropping of the Atomic bombs is fraught but there seems to be 3 key reasons that the Bombs were used.
- The Allies were very interested in ending the war: The War in Europe had ended several months earlier and the war in the Pacific was in its last stage. Russia had/was about to enter the war in Asia and the Western Powers were amassing a large invasion force that would storm Japan. The Nuclear Bombings were powerful tools in pressuring Japan to capitulate, but they were not sure how effective they would be. If you are familiar with the types of speeches that Churchill was giving when the invasion of Britain looked certain, you will be find many similarities between them and the propaganda that was being broadcast in Japan by the Government as they watched the Allied Forces prepare for a naval invasion and endured the bombings at the hands of the Allied bombers. The invasion of Japan could have proceeded without the bombings but the predicted causalities for the invading Allied forces and the defending Japanese (civilian and military) was projected into the millions. Thus the weapons were utilized to apply extra pressure to the Japanese government. World War II was a Total War, where in all aspects of the enemy state was viewed as a viable target because they performed vital aid that the state used to continue the war, the Farmer was just as valuable to the War Machine as the Machinist in the Military Factory, for where one provided bullets that armed the enemy soldier, the other provided food that kept him going. Such Indiscriminate weapons were powerful symbols that demonstrated the resolve of those using them.
- The Soviets were proving to be unreliable: FDR was interested in creating a new world where "spheres of Influence" would be a thing of the past, but with his passing and Churchill's removal from government, Stalin was hell bent on creating a Soviet Sphere of Influence and had been working to establish Soviet Puppet States in Eastern Europe. With their entrance into the Asian/Pacific Conflict the Allies were not sure where the victorious Soviet Armies would stop, and the detonation of such a powerful weapon would showcase a level of technological superiority over the Soviets that would help enforce the earlier agreements. In the days before the end of the Second World War, the Allies were uncertain that the Soviets would heed the agreed upon parallel that would divide the Korean Peninsula and they were relieved when the soviets did actually stop, however I am not familiar with any Soviet Historiography that states whether or not they entertained the idea of continuing on.
- The War in the Pacific had a very large racial component to it. The Euro-American powers were continuously surprised by the efficacy that the Japanese forces demonstrated and they paid the price for their underestimation of the Japanese. This created a dual impression on the minds of the Western peoples as the Japanese were "childlike monkeys" and "insidious supermen" at the same time, usually this is because the Allied forces would disregard intel or the skill of the forces they were about to face in battle and use the excuse that "they are so sneaky" when they lost. Comparisons of the Japanese to insects and vermin that needed to be exterminated were common at the time, and yes even while they were fighting against racists in Europe the Euro-Americans utilized Racist tactics in dealing with the Japanese. While the extent to which the Atomic Bombings were racially motivated is debatable, it is pertinent to notice that the "white european" Germans were not the subject of Atomic Bombings, and it is hard to imagine that such racist thought didn't somewhat influence the thoughts of the military planners. Earlier in the War such examples are recorded and it can be implied that it was at least present.*
I hope this has answered your question, if you would like me to clarify or expound on anything mentioned here please don't hesitate to ask me and I will do my best to facilitate an answer.
Best Regards,
R3N3
Sources/Suggested Readings on the Topic
War without Mercy By John W. Dower
Details the Racial components of the of the Pacific War
Five Days in August By Michael Gordin
Details the decisions that were weighed and made in the use of the Atomic Bombs on Japan
The Rising Sun By John Toland
Details the history of the War in the Pacific focusing heavily on the Japanese side of the events
Secret Weapons and World War II By Walter E. Grunden
Looks at the many Super Weapon projects that the myriad sides involved in WWII (USA, UK, Nazi, USSR, and Japan)
The Making of the Atomic Bomb By Richard Rhodes
Details the History of Atomic Research from the discovery of Radiation to the Atomic Bomb
Six Months in 1945 By Michael Dobbs
Details and lays out how the world went from WWII to the Cold War
*On the subject of Racial Stereotypes used in the Pacific War. It is important to note that the Racial Stereotypes employed by both the Americans and the Japanese were not new and didn't simply evaporate after the war. For the Japanese who portrayed the Americans as bestial demons during the war, the Japanese Religious tradition holds that such Demons "Oni" can also be benevolent protects, while the stereotype that they were lazy, decadent and corrupt would become dormant until it resurfaced during the economic tensions between Japan and America in the 1970's and 80's . As for the American Stereotypes, the Childish / Sneaky racial stereotype wasn't newly made for the Japanese, but instead was transferred from the Native Americans to the Japanese when it suited the purpose of the propaganda machine. It would also be transferred from the Japanese at the end of the war to the Russians/Soviets for the majority of the Cold War, and eventually transferred to the peoples of the Middle East when they became "the Enemy". Other aspects of the exotic/unknowable stereotypes would be buried until the economic tensions of the 1970's - 80's as mentioned earlier.