On February 7, 1855, Japan and Russia signed the Treaty of Commerce, Navigation and Delimitation, which confirmed the boundary between the islands of Etorofu and Uruppu. The Northern Territories, consisting of four islands of Etorofu, Kunashiri, Shikotan and Habomai, are an inherent territory of Japan, which have never been held by foreign countries. However, on August 9, 1945, the Soviet Union, in violation of the Neutrality Pact that was still in force between Japan and the Soviet Union, opened the war with Japan. Even after Japan accepted the Potsdam Declaration and made it clear its intent to surrender, Soviet forces continued its offensive against Japan and occupied all of the Four Northern Islands from 28 August 1945 to 5 September 1945.The Northern Territories have been under illegal occupation by the Soviet Union, and then Russia.
The Government of Japan has energetically been continuing negotiations with Russia based on its basic policy of resolving the issue of the attribution of the Four Northern Islands and concluding a peace treaty with Russia.