Japan and the Soviet Union restored diplomatic relations through a joint declaration in 1956.
The Soviet–Japanese Joint Declaration was signed in Moscow on 19 October 1956. It ended the state of war between the two countries and restored diplomatic relations, which had remained unresolved after Japan’s 1945 surrender. The declaration became effective on 12 December 1956.
The Soviet Union had declared war on Japan in August 1945 and took part in the final campaigns against Japanese forces in Manchuria, southern Sakhalin, and the Kuril Islands. Unlike most major Allied powers, it did not sign the 1951 Treaty of San Francisco. As a result, Japan and the Soviet Union required a separate agreement.
The declaration did not produce a comprehensive peace treaty or settle all territorial disputes. It stated that negotiations toward a peace treaty would continue. The unresolved status of the Kuril Islands contributed to the fact that Japan and Russia still had no formal peace treaty decades later.