yp11 wrote in
Then, in 1941 , when the Japanese Foreign Minister, Yosuke Matsuoka,
visited Moscow shortly before the German attack on the Soviet Union,
the two governments reached an agreement, called "a Neutrality Pact",
providing that either side would remain neutral if the other were
attacked by third parties. The Japanese kept their word and despite
[...]
On the other hand, Stalin broke the agreement with the Japanese as
soon as this was convenient to him, i.e. immediately after the
capitulation of Germany. In the final analysis Stalin didn't get much
out of it, namely he got the possession of southern Sakhalin and the
Kuriles. That's about all. The Americans prevented him from grabbing
part of Manchuria which was his initial intent. There was the
traditional sentimentality of the Americans about China which put them
squarely on the side of China (not knowing that it would soon become
Communist).

Yuri

I thought Stalin promised to attack Japan 3 months after May 9th, which is
exactly what he did. In a way, he was trying to keep both his promises for
as long as he could.

Interestingly, though, if the Americans expected Stalin to attack within
three months of May 9th, why would they be in such a hurry to drop the two
nuclear bombs...

Vassil