What forced Japan to surrender when the did was it:

A the US Atomic Bomb
B the fact that the Soviet Army was kicking their buts in China and would shortly be landing in Japan itself
C both

I think B because we were fire bombing them and that had little effect on the leaders clearly they did not care about civilian casualties but the prospect of being divided like Germany between the US and Soviet Union was more horrible than surrender to the Americans.

Originally Posted by Topmaul

What forced Japan to surrender when the did was it:

A the US Atomic Bomb
B the fact that the Soviet Army was kicking their buts in China and would shortly be landing in Japan itself
C both

I think B because we were fire bombing them and that had little effect on the leaders clearly they did not care about civilian casualties but the prospect of being divided like Germany between the US and Soviet Union was more horrible than surrender to the Americans.

I will go with neither and both.
For the most part Japan was looking for a way out from late 1944 and tend to think that the Atomic bombs finally nailed home the fact that it was all over however I am also of the opinion that the Russian invasion of Manchuria gave the Japanese the ability to get some "terms" that they would never have got had Russia not attacked.

Up until June-July 1945 the Western Allies demanded unconditional surrender which the Japanese were reluctant to accept, once the Russians announced they would be ready to invade Japan within a month the West suddenly started making accommodations for the Emperor which was acceptable to Japan (Interestingly enough there are many people that believe had the same offer been made in late 1944 early 1945 the Japanese would have accepted it ending the Pacific before the European one)..

I would say the bomb as well as many of the prominent people at home were telling them they were way out of line for what Japan did and should have done from the beginning of WWII.

a) They were getting their butts kicked
b) Banzai charging isn't going to stop that bomb

Just a guess but:
A) No where to run?
B) No where to hide?
C) All the above?

Lets look at why Japan lost WWII.

1. Too many wars going on at once - Japan made the same blunder Germany made by trying to get things over with quickly. Despite not having defeated the Chinese (both nationalist and communist) and went after the US. IIRC Japan had over 2/3s of its forces in China throughout most of the war.

2. Deciding to fight the US - There was little if any danger of the US coming to bit them. The cry was "no foriegn wars" from almost the entire US population. And they changed that mind set overnight by bombing Pearl Habor. They also did not seek out the American carriers when they had the chance, focusing on battleships instead which as the Pacific War later showed could easily be trumped by huge swarms of aircraft. The battleships during WWII were mostly good for only fire support roles and the very small number of ship to ship engagements.

3. Faulty doctrine - the IJN was way too into the big guns of their mighty battleships and heavy cruisers and often neglected the fact that aircraft carriers were the key to victory. Japanese commanders such as Isoroku Yamamoto saw the role that aircraft carriers were the key to victory but no one saw this until it was too late. The IJA was believed that things like Bushido and banzai charges against the enemy would bring them to victory. Just the opposite was proven when it was tried against machine guns and semi-auto rifles.

4. Loss of experienced personal - This happened a lot at both Midway and Guadalcanal among other places. The Japanese kept their experienced troops in the fight rather than sending them back to Japan to train raw recurits. The result was that these men were lost against the allies without passing on their experience to the troops in training and therefor the troops replacing them did not have a chance to benefit from the experience of the veteran troops. As a result the highly professional Japanese military turned into a ill trained and equiped rable.

5. Lack of good equipment - As far equipement goes the Japanese were a 30s military. The navy still believed in battleships and the Japanese did not have tanks that could be used for anything other than infantry-support. They lacked communcations as well as powerful artillery in many cases. AT weapons were also very poor.

6. Much weaker industrial output - the US alone had WAY more industrial capablities than Japan. Japan could not afford its losses against China and the US. It was bogged down in China and 2/3s of their ground forces were already stationed there and taking high losses against the Chinese and were already overstrenched when they attacked the US.

Russia had invaded parts of Japan and still holds the islands that they invaded.

The Atom bomb

Starvation

Lack of raw materials

The lack of fuel

Although Japan was looking for a way out of the war they still reluctant to part with their ill gotten gains

I vote for atomic bomb. Japan is rather small territory and wide use of WMD within its land could be fatal. They didn't know, how many bombs do Americans have so they took no risk and surrendered.

Japan would not have surrendered before the loss of Manchuria. When they lost it, they lost their largest army (the Kwantung Army) as well as their only remaining resource base. In addition, the war cabinet was vociferously against ending the war without some kind of victory. In spite of the fact that many Japanese were in favour of accepting the Allied surrender offers, the War Cabinet, which was composed of the only people in Japan with the power to end the war, was only going to accept a surrender with certain conditions attached. To that end, they continued to talk to the Soviets, trying to get the US led Allies to accept a surrender that included conditions like:

-no occupying armies on the Japanese home islands
-no war crimes tribunal
-the Emperor was not to be deposed, tried, or lose his status of a living god
-the Japanese Armed Forces were not to be disarmed.

Needless to say, these conditions were not acceptable to the US or the UK, and they were rejected out of hand. In spite of these rejections, peace feelers were often sent to the US and British governments. This went on with no change even after the first bomb was dropped. In fact, when compared to the fire bombings of Tokyo and Dresden, the Hiroshma bombing was considered to be quite tame.
All of this changed with the Soviet declaration of war, and the subsequent loss of Manchuria. Suddenly the Japanese were faced with the possibility of a Russian invasion from the north, and a US-UK-Canadian invasion from the south. They no longer had an army to defend themselves, and they no longer had the resources to build one. At this point, the manuvering began, with some members of the war cabinet killing themselves, and they were replaced by moderates. The second bomb was dropped, and the new cabinet signalled its intention to surrender to the Emperor, but there was a palace coup during which the militarists tried to keep the moderates from sending the surrender request to the Emperor. That coup was barely fought off, and in the end, the moderates had their way. But the timing of the surrender had very little to do with the atomic bomb, and everything to do with the realization that the war was lost when the Russians invaded Manchuria.

60 % Russian threat of total annihilation

40 % American threat of using the Atomic bomb on yet another city