Once again, people attempt to look back in hindsight, and determine what they THINK people should have done in a previous era.
In fact Hiroshima and Nagasaki saved millions of lives, both Japanese and American.
The bombing of Tokyo alone killed many more people than Hiroshima and Nagasaki combined. That INCLUDES those that died of radiation related causes as much as 40 years later.
An invasion of Japan would have cost a minimum of 5,000,000 JAPANESE lives. The Japanese government had trained school children, as young as the age of 5, to attack the invaders with sharpened bamboo sticks. They had trained, and encouraged women and girls to strap explosives to their bodies and to sacrifice themselves to blow up a single invading soldier.
We look back now, and can find evidence that perhaps (and I emphasize the PERHAPS) Japan COULD have been starved into submission. What is rarely mentioned however is what THAT would have done to the civilian population of Japan. The Japanese military was already taking a large proportion of the food supply available for the soldiers and sailors in their armed forces. Civilians were already on a virtually starvation diet level by July 1945.
The Japanese military tried very hard not to surrender EVEN AFTER HIROSHIMA AND NAGASAKI. In fact, a faction of the Army attempted to take the Emperor of Japan prisoner, in order to prevent his broadcast to the Japanese people telling them that Japan had no choice BUT to surrender.
The Japanese military were adamant that they would rather fight until everyone in Japan was dead, rather than surrender. The idea of surrender violated every precept that the Japanese military stood for. As far as they were concerned, any military person that surrendered was no longer even a human being, and deserved to no longer be treated as a human (which is why they treated captured prisoners of war so brutally).
It is so easy to “look back” and attempt to figure out what we would have done. We have knowledge that the leaders of this country did NOT have at the time. We have access to all of the records of the Japanese government, etc. that we did NOT have at that time.
In August 1945, Japan still had over 20,0000 military aircraft; over 7,000 naval armed naval vessels (including over 200 submarines with torpedos that were far superior to anything that we had) and they had almost 5 MILLION soldiers in Japan.
Hiroshima was a major military manufacturing area, as was Nagasaki. In addition, Hiroshima had 5 major Japanese military installations, with well over 400,000 soldier/sailors, within 10 miles of downtown Hiroshima. Both of them were, by all definitions, legitimate military targets.
At that time, Japan still occupied approximately 1/3 of China, all of Manchuria, all of Korea and had vast military potential to resist invasion.
The decision was made to utilize the bomb, and it was entirely justifiable at the time.
If the bomb had been ready earlier, it would have been used on Berlin, again justifiably.