The soviets didn't fight the japanese till the germans were defeated, their one-front war continued to be one front, just on the east. They declared war on a nearly destroyed japan one week before the end of the war, after the US had fought them all the way across the pacific, destroyed their air force, their navy, their cities, most of their industry, and atomic bombed them. Whoopee - doo.
Here's the part you "forgot" to cite from the wiki article:
In other words, the "neutrality pact" simply codified exactly what I said was the reasons for no desire for engagement on both sides, and either side would have abrogated it in a second if it were to their advantage - in fact, that's what did indeed happen as you yourself admit when the soviets invaded japan. Incidentally, the neutrality treaty also included soviet recognition of the barbarously acquired japanese colony of "manchuko" (manchuria) in northeast occupied china - did you know THAT?
As to that invasion, it represents one aspect of the last act in franklin roosevelt's long disastrous administration, the yalta conference, not only selling out eastern europe to soviet colonialism, but inviting them in to attack japan only because of his doubts about whether the atomic bomb would work. But the atomic bomb was shown to work with the Trinity test on July 16, 1945 - the need for the soviets disappeared at that moment, but FDR inexplicably failed to call off the soviets. In fact, they didn't invade till after the hiroshima bombing, and the same day as the nagasaki bombing.
