Amazingly, some people claim that the dropping of the two atomic bombs did not contribute to Japan's surrender in World War II, and that it was only the USSR's declaration of war that got them to give up.
One even proclaimed that "Despite all of that anti-American propaganda they produced, they still surrendered to us, specifically and unconditionally, and they would have done so without Little Boy or Fat Man getting loaded onto a bomber. You might say thats hindsight 20/20, but there is no argument against the fact that Hiroshima and Nagasaki were spared during the firebombing campaigns that ravaged virtually every Japanese city, and they just so happened to he the most nukeable cities from a devastation/observation standpoint. That level of premeditation isnt military strategy, its showmanship." (this person also claimed that the invasion of the main Japanese islands would not have been bloody; the Battle of Okinawa only saw so many deaths because of the geography of the island, ignoring the fact that Japanese civilians were training to resist the upcoming invasion; and that the Kyūjō incident was not unique and happened because people did not want to lose power)
All this seems to be motivated by anti-American sentiment - if one can reframe the dropping of the atomic bombs as just a way to intimidate the Soviet Union, rather than a way to end the war sooner, the US can be painted as evil.
While historians might disagree over the relative importance of both factors, the overwhelming majority seem to agree that the atomic bomb played at least some role:
"There is no doubt that the double shock of the atomic bombing of Hiroshima and Nagasaki and the Soviet invasion of Manchuria were both very important in prompting Japan to surrender...
Robert Butow... argued in 1954 that the atomic bombing of Hiroshima and Nagasaki and the Soviet declaration of war created “that unusual atmosphere in which the theretofore static factor of the Emperor could be made active in such an extraordinary way as to work what was virtually a political miracle.”... [Sadao] Asada emphasizes the shock of the atomic bombs on the military’s confidence...
In the end, the reasons for Japan’s failure to respond the Potsdam Proclamation were twofold: first, because Stalin had not signed the Allied ultimatum, Foreign Minister Togo wanted to ascertain the Soviet response to Tokyo’s request for mediation before Japan replied; and second, the overwhelming majority of Japanese military officers, especially in the army, were still in favor of fighting to the bitter end, and the Suzuki cabinet was unable to prevail over their resistance.
Therefore, in the opinion of Emperor Hirohito, Kido, and the peace faction, there was no doubt that the combination of two catastrophic events —the atomic bombs dropped over Hiroshima on August 6 and Nagasaki on August 9; and the Soviet declaration of war against Japan on August 9— provided the final impetus for Japan’s decision to end the war...
With regard to the question of which had more effect on Japan’s surrender decision, the atomic bombs or Soviet entry into the war, Kido’s postwar statements were fairly consistent. When the investigative team from the US Strategic Bombing Survey asked Kido this very question on November 10, 1945, Kido answered that it was hard to tell exactly which had more impact. During his interview with Japanese historian Oi Atsushi at Sugamo Prison in April 1950, Kido stated...
'I think that the atomic bombs alone could have allowed us to terminate the war.'...
Kawabe [Torashiro] wrote in his memoir, “I felt the atomic bomb struck me hard on one cheek, and immediately afterwards the Soviet declaration of war hit me with full force on the other cheek.” Perhaps, historians will never be able to agree on the exact weight to assign to these two extraordinary events. The recollections of Japanese eyewitnesses suggest that the bombings and Soviet declaration of war happened so close together that it was humanly impossible to separate their psychological impacts...
According to Togo’s memoir, during the morning of August 8, Togo met with the emperor and reported that an atomic bomb had been used against Hiroshima. Togo proposed, “This should be used as an opportunity to decide for the earliest possible termination of the war.” The emperor agreed with the foreign minister and said, “Now that this sort of weapon has been used, it is becoming increasingly impossible to continue the war. I do not think it is a good idea to miss an opportunity to end the war by attempting to secure advantageous conditions. Besides, even if we try to discuss terms, I am afraid we won’t be able to come to an agreement. Therefore, I hope you will take measures that will conclude the war as soon as possible.”
Thus, emphasizing the need to end the war at the earliest possible opportunity, the emperor asked Foreign Minister Togo to convey his opinion to Prime Minister Suzuki. Togo immediately contacted Kido and the prime minister and requested that they convene a meeting of the Supreme War Leadership Council."
--- Emperor Hirohito and the Pacific War / Noriko Kawamura
