It was necessary to use that.Not only to save American lives also Japanese lives.
There were three alternatives to the Atomic bombing of Japan with it's attendant 200,000 (approx) casualties
Firstly, hold off on the Nukes and bomb the Japanese into submission using conventional bombs. Remember that 120,000 people died in one raid on Tokyo(Tokyo fire bombing) and it appeared to have no effect on the Japanese will to continue fighting.
Secondly, invade the Japanese home islands where the civilian population were being trained to take on the invaders with carving knives attached to broom handles,as well as new volunteer force was made.
The estimates for casualties, based on what happened on Iwo Zima,Okinawa and Saipan.Remember in these 3 islands,considered Japanese home land,Japanese soldiers fought to death,even there were many hide outs of Japanese soldiers who did not surrender.There US marines and Army had to fight a lot.
And also any one should not forget land based Kamikazes,they resulted heavy damage on US navy in Okinawa and Iwo Zima,by August Japanese invented "Okha" suicide crafts,it could carry 1200 KG bomb,it was far better than normal aircrafts that Japan used for Kamikazes.
Zero plane,attached with 250 Kg bomb,it was easy to shoot down,as it lacked armour.
Same to other planes,Japanese pilots by 1945 was ill trained than Americans,most of the Kamikazes were shot down on way by US fighter or anti-aircraft guns.But Okha was very fast.
Thirdly, to starve them out.
Blockade the Japanese home ports whilst continuing the ground war in China-Burma-India and wait for them to drop from exhaustion. Sounds great doesn't it? Minimal casualties, no-one killed by iron or atomic bombs falling from the sky, everyone happy to see the end of the war. Let's look at the likely final scenario.
After the war had been won in 1946 or 7 with the pitiful sight of the last Japanese soldiers dropping from starvation on the home islands, and the inevitable pictures taken as the victorious Allied soldiers marched through a country blighted by the death of 90% of it's civilian population, bodies putrefying and unburied on the streets, dysentery, cholera and various other diseases rampant among the few remaining lucky survivors, how long would it have been before the Bleeding Heart Liberals started comparing Truman to Hitler and claiming that he had treated the Japanese as bad as Germany had treated the Jews by locking them up and giving them no means of sustenance?
And then when it turns out that he had a bomb that would have shown the might of the USA to the world and maybe one or two of them dropped on strategic towns may have forced the Japanese to surrender early and forgo the horrors of 2 years of starvation. OH MY, he would have been pilloried.
So which of the 4 possible methods would you have chosen? Would you have the brass cojones necessary to pick the one with the least total casualties?
So it seems atomic bombing was right according to contemporary situation.Also US warned Japan,that if Japan would not surrender,they(US) would use a new very powerful,and leaflets were also dropped,still Japanese decided to continue war.
Even after drop of atom bombs,some Japanese Generals decided to continue fighting.
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