What made Japan surrender in WW2?

[STR]

If this is the truth, does it mean that the war would have ended with the Soviet's entry regardless of the bombing?

Russia stronk, will all war itself. /s

The Soviets were years away from building a Navy sufficiently large to threaten Japan.

does it mean that the bombing was unnecessary?

The nuclear bombs weren't just about leveling cities. The allies already proved their ability to lay waste to cities. What the nuclear bombs changed was how many aircraft you needed to do that level of damage.

Whereas before, you just needed to worry about large formations. You now had to intercept every single lone bomber. Especially since Japan had no way of knowing the bombs weighed 5 tons and *only* the B-29 could carry them.

That's really hard on a country low on pilots, aircraft and fuel. They already had to ration as-is.

Does it mean that the conventional bombing of Tokyo was unnecessary?

America could only crank out 1-2 bombs a month. The 3rd bomb wouldn't have been ready until the end of August, the next batch September/October. There were plans to scale up beyond that (and we all saw how big the production line got in the Cold War), but conventional weapons would still be needed to keep up pressure.

Also, nuclear and conventional weapons are not either/or propositions, even today. They are complimentary.

All the US really needed to do was blockade and wait for Stalin?

Wait for Stalin to do...what? Russia had nothing in the east. They were entirely committed to the west. It would have taken months just to stage men and material, and that's if the Siberian winter cooperated. And again, the USSR had an even worse navy than late war Japan.

Meanwhile, the USA *did* have a navy and air force already in theater and Japan had no doubts they had the men and material to finish the job and that was *before* America turned the air war calculus on its head.

Japan knew the war was lost. It just wasn't ready for unconditional surrender. They were trying to negotiate to preserve something of the empire. And in the end, they got their #1 wish: the emperor was not deposed. If you're going for a contrarian explanation for the end of the war, that's the one to buy into. That Japan didn't surrender until America guaranteed the imperial family.

In reality, it all contributed. Even (though least of all) the USSR.

 

[Bad Thoughts]

Wait for Stalin to do...what? Russia had nothing in the east. They were entirely committed to the west. It would have taken months just to stage men and material, and that's if the Siberian winter cooperated. And again, the USSR had an even worse navy than late war Japan.

Meanwhile, the USA *did* have a navy and air force already in theater and Japan had no doubts they had the men and material to finish the job and that was *before* America turned the air war calculus on its head.

Whether then US developed the bomb or not is really not important to the question: the USSR was unable to project power, either by air or sea, to threaten Japan directly. The Manchurian offensive was by this point a sideshow by what was essential a land power. As you point out, the US was already positioned to starve Japan of the essentials to make war, even using conventional means. Conversely, the USSR's fleet of long-range bombers was small and vulnerable, it's IL-2s could not be a major threat because of range and payload capacity.

 

[StarCruiser]

Yep - the Soviets were VERY "stronk" on land and they had a fairly good tactical Air Force but, lacked for any significant naval forces or strategic air power.

Very much a land power at that time...

 

[STR]

Fun fact: it cost more to develop the B-29 ($3B+) than the Manhattan Project ($2B). Just as the Manhattan project had two parallel designs (uranium gun and plutonium implosion) the bomber project developed the ambitious B-29 and the safer B-32 (a development of the B-24) as a fallback.