Do you really think any European country was in shape to face Japan? Russia experienced a famine right after Germany capitulated, they almost lost Moscow, they received billions of dollars from the US to be able to finish the war.
I think just trying to mobilize their troops to the east would have been unimaginable
Russia invaded and occupied the Sakhalin islands near the end of World War II. Native Japanese were allowed to leave, as I understand it.
"Japan invaded the northern parts of Sakhalin, and ruled the entire island from 1918 to 1925. Russia has held all of the island since seizing the Japanese portion in the final days of World War II in 1945, as well as all of the Kurils."
