After the battle was stopped on August 15, 1945, the Soviet Union illegally invaded the Northern Territories and aimed to occupy Hokkaido.
However, at the order of General Kiichiro Higuchi, he defeated the Soviet troops moving south on Shumshu Island.
Before the Edo period, Sakhalin was thought to be a peninsula, and Mamiya Rinzō of the Edo Shogunate discovered it as an island by survey.
Under the Japan-Russia Treaty of 1855, the border between Japan and Russia was set between Etorofu Island and Urup Island, and Sakhalin was designated as a mixed-use area between Japan and Russia.
In 1875, the Sakhalin-Kuril Islands Exchange Treaty was signed, and instead of abandoning Sakhalin, Japan had the Kuril Islands handed over from Russia.
The result of the Treaty of Portsmouth was signed in 1905 as a peace treaty for the Russo-Japanese War. South Sakhalin south of 50 degrees north latitude became the territory of Japan.
In 1945, at the Yalta Conference, the United States and Britain admitted to "hand over" the Kuril Islands to the Soviet Union in exchange for the Soviet Union's participation in Japan.
In the first place, the Soviet Union participates with the United States and Great Britain in the Atlantic Charter, which does not allow the expansion of territory due to war
Nevertheless, there are criticisms about the invasion of the Northern Territories in the form of expanding the territory in the war.
No peace treaty has been signed with the Soviet Union, and Sakhalin is still a landless land. The same applies to the four northern islands and the Kuril Islands.