An interesting compilation. Since it comes from Soviet sources dated 1952, it’s not clear how accurate it is, but I would guess it is fairly so. This document has been cited in various historical sources.
One thing at the end of the list, though; it states that Russia was Japan’s “ally” during most of the war. That is simply not true. The two parties maintained a strictly correct neutrality toward each other, but never were they “allies.”
Yeah. If I remember right the Soviets even interned our air crews, didn’t they?
Russia/USSR had three scores to settle in WWII, and they succeeded in settling two of them. The three scores were, in chronological order, the Japanese beating the Czarist Navy in 1905, the British getting control of the middle east oil fields in WWI, and the Nazis reneging on their neutrality pact.
My guess, and it's only a guess, is that Stalin thought that after he signed the neutrality pact, Hitler would concentrate on the west until Britain was brought under Nazi hegemony, perhaps completely conquered. In the meantime, Stalin could take the oil fields for himself, and then catch the Japanese flat-footed in the Kuriles in 1941, perhaps even taking Hokkaido. He could then decide how to handle Hitler, whether to take him for an ally against the United States with Stalin taking Alaska while Hitler took over the Atlantic and gained allies in Latin America, or to fight Hitler head-on in Poland while convincing Japan to lay off Hawaii, and getting America into the European war.
All that went out the window when Britain didn't buckle under the Nazi attacks, Russia didn't get the oil fields, and then Hitler reneged and invaded in June 1941: that put avenging against Japan on the back burner, and so Stalin claimed neutrality with Japan during 99% of the war. This was because Stalin had bigger fish to fry: he had to do what Alexander I had done to Napoleon 130 years earlier, which was to make Hitler fight for every square inch of ground, stretch out the enemy supply lines to the breaking point, then let the winter conquer the enemy. Just as Alexander and Napoleon went from allies to moral enemies, so did Stalin and Hitler.
Stalin's mistake with Japan was that he actually kept his word given at Yalta, and waited three months from the end of the European war to invade. He could just as easily have broken his word--he was a Communist after all, integrity is not their strong suit--and invaded the Kuriles and Hokkaido in July, presenting Truman and Churchill a fait accompli at Potsdam. Why he didn't is one of those questions for which there will never be a good answer.