You bring up some good points that make people think a bit more, nothing
wrong with that at all, thats how i learn about new stuff all the time.
My thought on the Russian and Japanese realtionship was always one of
turmoil like the others say. There was the naval victory Japan had against Russia decades earlier. Then in '39 Japan invaded Russia and got their butts
kicked big time.
But like you i wonder why they did pick Russia as the go between for talks.
Maybe they thought they were our closest ally that would of been more willing to help??
Can you imagine them trying to use China or Australia, they both had bad gruges against Japan.