What areas were fought over in the war fought by the Japanese Fourth Army?
Fourth Army (Japan) The Japanese 4th Army (第4軍 , Dai-yon gun ) was an army of the Imperial Japanese Army based in Manchukuo from the Russo-Japanese War until the end of World War II.
Invasion of South Sakhalin The Invasion of South Sakhalin also called the Battle of Sakhalin (Russian: Южно-Сахалинская операция) and (Japanese: 樺太の戦い) was the Soviet invasion of the Japanese territorial portion of Sakhalin island known as Karafuto Prefecture. The invasion was part of the Soviet–Japanese War (1945).