So Japan did not torpedo US Liberty ships headed to Russia, and various other surprising things. (Japan obeyed international treaties to the letter, but did not follow any human rights conventions.)
Of course, at the end of WW2, Russia turned their vast army and artillery eastward, and annihiliated the Japanese army.
Source: I study WW2.
Of the ~1,092,400 Japanese soldiers facing Russia, only 22,300-23,600 were killed according to Japan (Russia places the figure at 83,737):
Not according to them[1]:
"More than ever before, the historical record confirms what those soldiers knew in their gut: Hiroshima and Nagasaki, hideous as they were, shortened the war that Japan had begun and saved an immensity of lives. Far from considering itself essentially defeated, the Japanese military was preparing for an Allied assault with a massive buildup in the south. It was only the shock of the atomic blasts that enabled Japanese leaders who wanted to stop the fighting to successfully press for a surrender.
"'We of the peace party were assisted by the atomic bomb in our endeavor to end the war,' Kido Koichi, one of Emperor Hirohito's closest aides, later recalled. Hisatsune Sakomizu, the chief Cabinet secretary, called the bomb 'a golden opportunity given by heaven for Japan to end the war.'"
[1] http://archive.boston.com/news/globe/editorial_opinion/oped/...
If I'm not mistaken, they hadn't signed any.
This makes me curious. What other things?
Stalin only agreed to break the non-aggression pact once it became clear that no invasion from the west was coming, which was fairly late in the war (Yalta).