Remember the oil embargo of 1937? Japan attacked the U.S. and U.K. out of desperation for oil, and steel. They were on the verge of collapse. There was no way they could invade the Soviet Union. It just couldn’t be done. The East Indies were invaded for their oil, and Pearle was hit to take out the U.S. fleet and bring the US to the negotiation table. Had there been no embargo, there would have been no Pearle Harbor.
If Japan had the oil, would it have invaded the Soviet Union? The Axis Nations were originally Hitler’s anti-Comintern Pact, signed between Germany and Japan on November 25, 1936. It was basically an alliance against the Soviet Union. Still, the answer is no, not after their defeat against the Soviets in the battle of Khalkhin-Gol in 1939. Germany formed an alliance with the USSR against Poland 1 day after the Japanese lost the battle, and after Hitler had offered for Poland to join the anti-Comintern Pact in exchange for Danzig.
Why should the Japanese have trusted Hitler and gone to his aid after being stabbed in the back, and when they had no vital national interest in invading the Soviet Union?
Why should Japanese soldiers fight a war they couldn’t win, for a cause they didn’t believe in, only to have the Bolsheviks march into Tokyo, and rape, pillage, and burn the city to the ground, with millions of Japanese being sent to the Gulags, never to be seen again?
The Japanese didn’t surrender after being nuked twice, but they did surrender after the Soviets invaded Manchuria. Why? Because there are indeed fates worse than death.