Political map of Russia & the former Soviet Union 20 January 1925 (Soviet-Japanese Peace Treaty): On January 20, 1925, the Japanese finally signed a Peace Treaty with the Soviet Union (Japan during the Siberian Intervention) and agreed to withdraw from North Sakhalin in exchange for mining concessions. Over the next months, the Soviets would suppress the remaining resistance in Siberia. After claiming about 15 million lives, the Russian Civil War was effectively at an end.