Japan discovered and surveyed the Northern Territories before the Russians arrived there and had established effective control over the four islands by the early 19th century at the latest. In the first half of the 19th century, Russia also recognized Urup (the island located immediately north of Etorofu Island) as the southern limit of their territory in this area. The Treaty of Commerce, Navigation and Delimitation between Japan and Russia confirmed the already established natural boundaries, drawing the boundary between the islands of Etorofu and Uruppu.

In accordance with the Treaty for the Exchange of Sakhalin for the Kurile Islands, Japan received all the rights to the Kurile Islands (in this treaty, the Kurile Islands were taken to be a string of 18 islands, Shumushu Island being farthest north and Uruppu Island being the farthest to the south.) from Russia, in exchange for the cession of the rights on the island of Karafuto (Sakhalin).

The Portsmouth Peace Treaty was concluded after the end of the war between Japan and Russia and ceded to Japan from Russia the part of the Karafuto Island that lies south of the 50th degree of north latitude.

In August 1941, the leaders of the United States and the United Kingdom signed the Atlantic Charter that would serve as the guiding principles for the Allies in the Second World War, The Charter clearly set forth the principle that these two countries sought no territorial expansion by means of war.(the Soviet Union proclaimed allegiance to the Charter in September of that year).
The Cairo Declaration of 1943 affirmed this principle of the Atlantic Charter and stated that Japan would be expelled from “territories which she has taken by violence and greed” and the other territories. However, in view of the historical background, it is clear that the Four Northern Islands do not constitute territories that Japan seized “by violence and greed”.

The Potsdam Declarationstated that the terms of the Cairo Declaration which stipulated that Japan would be expelled from “territories which she had taken by violence and greed” should be carried out, and that Japanese sovereignty should be limited to the islands of Honshu, Hokkaido, Kyushu and Shikoku and such minor islands as Allies determine.
However, the Soviet Union, ignoring the Neutrality Pact that was still in force between Japan and the Soviet Union, opened the war with Japanon August 9th, 1945. The Soviet Union continued its offensive against Japan after the Potsdam Declaration was accepted by Japan and illegally occupyied the Four Northern Territories between August 28th and September 5th of that year ( Japanese army did not put any resistance to the occupation of the Northern Territories, and it was carried out without violence).

Under the San Francisco Peace Treaty, Japan renounced all right, title and claim to the Kurile Islands and the part of Sakhalin over which Japan acquired sovereignty as a consequence of the treaty of Portsmouth. However, the Four Northern Islands are not included in the Kurile Islands. Furthermore, the Soviet Union did not sign the San Francisco Peace Treaty and is not in a position to claim its rights under the Treaty.

There was no prospect for the two countries’ reaching an agreement on the territorial issue, excluding the Habomai Islands and Shikotan Island. Therefore, the two countries signed the Japan-Soviet Joint Declaration instead of a peace treaty. The Declaration officially ended the state of war and restored diplomatic relation between them, among other provisions.
→Both parties agreed to continue peace treaty negotiations.
→The Soviet Union agreed to hand over the Habomai Islands and Shikotan Island to Japan after the conclusion of a peace treaty.

This was the first time that the Soviet Union acknowledged in writing the existence of the issue of territorial demarcation, mentioning the concrete names of the four islands.

The Tokyo Declaration

• （A）defined the territorial issue as being an issue of the attribution of the Four Northern Islands;
  
• （B）clearly set out that Japan and Russia should conclude a peace treaty by solving the issue of the attribution of the four islands and thereby fully normalize bilateral relations; and
  
• （C）set out clear negotiation guidelines; the territorial issue should be resolved (ⅰ)on the basis of historical and legal facts, (ⅱ)based on the documents to which both parties agreed, and (ⅲ)based on the principles of law and justice.
  

The Tokyo Declaration also confirmed that all treaties and the other international agreements between Japan and the Soviet Union continued to be applied for the relations between Japan and Russia.

• （A）This statement difined the Japan-Soviet Joint Declaration of 1956 as the starting point of the negotiating process and confirmed its legal validity in writing.
  
• （B）Leaders reaffirmed common recognition between Japan and Russia that, on the basis of the Tokyo Declaration, a peace treaty should be concluded by solving the issue of attribution of the four islands.
  

• （A）In the Joint Statement both leaders affirmed their determination to resolve the issue of the attribution of the four islands and conclude a peace treaty as soon as possible, thereby completely normalizing relations between the two countries.
  
• （B）The Japan-Russia Action Plan specifically mentioned the 1956 Japan-Soviet Joint Declaration, the 1993 Tokyo Declaration and the 2001 Irkutsk Statement and it was affirmed in the Action Plan that these, in condition with other agreements, were the basis for future peace treaty negotiations.
  

• （A）In the Joint Statement, both leaders shared their recognition that the absence of a peace treaty between Japan and Russia 67 years after the end of World War II was an unnatural state of affairs. They expressed their determination to conclude a peace treaty by overcoming the gap between their positions and finally resolving the issue (the attribution of the four islands) which was determined to the resolved both in the 2003 Joint Statement and Action Plan.
  
• （B）Both leaders agreed to give instruction to their respective Ministries of Foreign Affairs to accelerate the negotiations toward elaborating a mutually acceptable solution of the peace treaty issue.
  

As a result of candid and extremely in depth discussions over a long period of time on the issue of peace treaty between only the leaders, the two they expressed their sincere determination to resolve this issue.
Based thereon, they agreed to commence discussions on conducting joint economic activities on the Four Northern Islands under a special arrangement.

The two leaders agreed to “accelerate negotiations on a peace treaty on the basis of the Japan-Soviet Joint Declaration of 1956.”

The two leaders confirmed that they would firmly work on the peace treaty negotiations based on the various agreements created by the two sides so far, including the one between the two leaders in Singapore in 2018.

Under Four-Island Exchange Program, mutual visits between Japanese citizens and Russian residents of the Northern Territories without a passport or a visa have been arranged in order to promote mutual understanding and contribute to the settlement of the territorial issues until the Northern Territories issue is resolved. The program has been conducted since 1992.

Free visits have been conducted on humanitarian grounds for former island residents and their family members (Japanese citizens) to visit the Northern territories in the most simplified manner. The program has been organized by the organization of former residents since 1999 with support from the Japanese government.

Visits to graves have been conducted with an identity document on humanitarian grounds. The program has been organized by the Hokkaido Prefectural Government in 52 graves in the Four Northern Islands since 1964.