Is it true that the Japanese were extremely stubborn and that kept fighting even against the odds?

From the onset of the US offensive throughout the Pacific Campaign, the Japanese often fought to the last man or committed ritual suicide before surrendering. So yes they were extremely stubborn and kept fighting against all odds. Any argument against this fact is pathetic.

I heard that the US "had no choice" but to bomb them because the Japanese wouldn't surrender.

Of course the US had a choice. There were multiple different options for how to continue the war with Japan. Traditional bombing, blockade, mainland invasion, ect. Much of the Japanese government refused to surrender. Others were trying to figure out the best way how.

In the end we dropped the bombs, the Soviets declared war on Japan, and Japan surrendered.

Below is the hypothetical scenario of what the Invasion of Mainland Japan might have looked like. Much of these estimates were created after the statistics were gathered from the Battle of Okinawa.

Over the 82 day battle (one of the longest of WWII) the Japanese sacrificed nearly 100,000 men for only 3.5 miles of land…. think about that for moment. The United States suffered 79,000 casualties 12,500 of which were KIA/MIA in both the land and sea battles for Okinawa. All of that for just 3.5 miles of land... the Japanese were that fanatical.

The planned Invasion of the Japanese mainland was named Operation Downfall. It consisted of two separate parts Operation Olympic (Invasion of southern Island Kyushu) and Operation Coronet (Invasion of the Kanto plain near Tokyo).

Olympic would come first. Established Airbases on Kyushu would provide ample air cover for the later Coronet. 14 Combat Division of Soldiers and Marines would carry out this amphibious island assault during the morning of November 1st, 1945. The Japanese would have 790,000 young, fanatical Imperial Soldiers defending this home Island, outnumbering the invader 3 to 2. The defenders were ordered to fight to the death from the beaches and all the way into the islands interior. Imagine Iwo Jima x20. The mountains of Kyushu became a network of underground bunkers and machine gun nests. It is estimated that 1,000 Japanese and Americans would die every hour in the initial assault of Kyushu. General Douglas MacArthur’s intelligence staff estimated that the U.S. would suffer 250,00 combat casualties on Kyushu alone. This was a rather conservative estimate. The invasion would take four months and if all went well Coronet would be launched.

Coronet would have been the most massive amphibious Invasion in human history 5X larger than D-Day with 28 Combat Infantry Divisions landing on Honshu along the eastern coastline of Tokyo, and the 1 million Japanese defenders (excluding the millions of civilians trained to fight to the death) who knew exactly where the US Soldiers/Marines would land. The most costly mistake of US intelligence would be the estimated amount of Japanese airpower and suicide Kamikaze pilots that the US Ground forces and Navy would face. Blind estimates stated that the Japanese has 2,000 planes left. Japanese military documents captured after the war showed that the Japanese Army and Navy had some 12,000 planes stockpiled(Everything from crop planes with bombs attached to new Zeros). The majority of which would be used for Kamikaze attacks on the US Navy. The plan was to send wave after wave of 200-300 Kamikazes every hour to soak up the Navy's anti-aircraft ammunition, before launching constant Kamikaze waves which the Japanese hoped they could keep up for 10 days straight. This attack would most likely have destroyed at least half of the US Navy forcing a retreat and abandonment of US ground forces, much like Guadalcanal.

Overall the united stated would suffer a 1,000,000 casualties in Operation Downfall. Easily 10’s of Millions of Japanese civilians would of died in the conflict. These are rather conservative estimates.

This escalation would have convinced the President and his advisors to drop the Nuclear Bombs anyway. Simply, WWII doesn’t end without the dropping of the bombs. And the fact that we had to drop two should be evidence enough that Japan was not ready to surrender.

Sources

The Ultimate Battle - Bill Sloan

Tenozan: Okinawa and the Atomic Bombs – George Fiefer

Hell to Pay: Operation Downfall and the Invasion of Japan, 1945-1947 - D. M. Giangreco

Downfall: The End of the Imperial Japanese Empire - Richard B. Frank

Multiple articles online about Operation Downfall/Olympic/Coronet. Can list if requested.

This is a very popular question on AskHistorians, and it has its own section in our FAQ. There's always more room for more discussion, but this is a great start:

http://www.reddit.com/r/AskHistorians/wiki/wwii#wiki_the_atomic_bombs

Like many complex historical statements, it's not quite true.

What makes it not quite true? Well, there were choices. The atomic bombs were one of several options on the table. Including diplomatic ones. The situation of the Japanese high command in the summer of 1945 was that it was split. The hardcore militarists wanted to keep fighting even if it was suicide. There was a "peace" faction that wanted to end the war quickly, but only if they had guarantees about the state of the Imperial house after surrender. In the summer of 1945 they were attempting to engage the (then-neutral) Soviet Union as a mediator with the United States, with the idea that they could negotiate a compromised peace position that would permit the Japanese to maintain the Emperor. The Soviets had already secretly committed to breaking their neutrality with the Japanese in exchange for territory, so they strung them along. The United States was aware of these quasi-negotiations because they were able to intercept and decrypt Japanese diplomatic codes. No less peaceniks than Winston Churchill and the Secretary of War encouraged Truman to reconsider and clarify the postwar status of the Emperor in the Potsdam Declaration, because they thought it was probably the only major item keeping the Japanese from surrendering. Other Truman advisors, such as the Secretary of State, encouraged Truman to maintain his demand, knowing it would require the use of the atomic bomb and maybe invasion.

So this goes very much against the standard, "we only did it because there was no other option" narrative. Separately one could also consider options other than dropping the first atomic bomb on the center a mostly-civilian city (e.g. a "demonstration" bomb), which was briefly deliberated at levels lower than Truman, or by choosing exclusively military targets (that would be less impressive in terms of death toll and destruction, but maintain higher moral authority). In fact I think there is evidence that Truman misunderstood Hiroshima's mostly-civilian status. Lastly, one could imagine a situation in which two bombs were not dropped within three days of each other — which was barely enough time for the Japanese high command to even verify that the weapon used was in fact an atomic bomb. The scheduling was chosen largely because of the weather, not strategic reasons. There are scholars who have argued that Hiroshima might have been justified, but Nagasaki might not have been.

One can justify the US position in using the bomb, if one is inclined. They had made a new weapon and expected to use it. They had arguably crossed whatever moral line there was when they started deliberating targeting civilians in their ruinous firebombing campaign which destroyed 67 Japanese cities before Hiroshima and Nagasaki. Truman's knowledge of the bomb's effects was extremely limited and he was acting on the advise of people who he trusted. The top scientists believed that only a use of the bomb with heavy casualties would convince the world to pay attention to the power of nuclear weapons. And so on. But one should not believe anyone who tells you that they had "no choice" — historical actors generally do have choices, and in this case it is easy to document the decisions (choices) that were made.

That being said, the notion that there was a big "decision" to use the bomb, that Truman deliberated over it much or saw it in terms of a calculus of saved versus spent lives, is entirely false. There was no real decision over whether to use the bomb. The decision was over how it might be used, when it might be used, what types of targets it might be used against, and so forth. Almost everyone involved in the creation of the bomb expected it to be used, almost everyone at the high levels of US government saw it as a good thing. There were exceptions, notably those among the military — Eisenhower thought it was unnecessary, for example. There were many others in the military who would later argue that the bomb didn't have to be used, and the US Strategic Bombing Survey itself concluded that "even without the atomic bombing attacks, air supremacy over Japan could have exerted sufficient pressure to bring about unconditional surrender and obviate the need for invasion".

Though I am not sure I agree with his overall thesis, Tsuyoshi Hasegawa's Racing the Enemy is one of the more enlightening and interesting books written on the US, Soviet, and Japan positions in the final days of World War II. He is very good at emphasizing the choices made, and the complexity of the reasoning behind them.