The Kuril islands
How the Kuril islands went from Japanese to Soviet hands in 1945, and why Japan and Russia still dispute them.
Watching a Yes Theory video following my recent trip to Japan turned into a 2-hour session of researching about an archipelago dispute on the Pacific Ocean between Japan and Russia 🙃.
The Kuril islands are an archipelago of 56 islands (plus many minor islets), mostly volcanic, stretching about 1,300 km from Hokkaido, Japan’s northern “big” island, to Kamchatka in Russia.
Ainu people
These islands used to be the home to the Ainu people - they lived there from early times, but written records from before the 17th century are scarce. The Japanese took control of the islands during the Edo period. A Japanese map from 1644 (the Shōhō map, of the Matsumae domain) shows 39 islands northeast of Hokkaido as part of Japan.
From the 17th century up until the late 19th century Ainu and Japanese co-existed in this archipelago. After the 1875 Treaty of St Petersburg (see below), the Japanese started to forcefully assimilate the native Ainu by:
- Relocating the entire Kuril Ainu population (97 people) to Shikotan in 1884
- Giving the natives Japanese names
- Forcing them to abandon religious practices
The 1855 Treaty of Shimoda set the border between Russia and Japan between Iturup and Urup, giving Japan the four southern islands. In the 1875 Treaty of St Petersburg Russia gave up the rest of the chain in exchange for uncontested control of Sakhalin.
Up until WWII these islands were internationally recognized as Japanese and inhabited by “Japanese” people.
WWII
During WWII these islands proved to be strategically important to the Japanese. Navy ships assembled in Hitokappu Bay (Tankan Bay), on Iturup (South Kuril), by November 22 and sailed from there on November 26 to strike Pearl Harbor on the morning of December 7, 1941 (Hawaii time), the event that (finally) made the US join the world war.
The Yalta Agreement was a meeting held between Feb 4 - Feb 11 1945 in the Soviet Union between the US (represented by Franklin D. Roosevelt), the UK (represented by Winston Churchill), and the Soviet Union (represented by Joseph Stalin). The goal was to discuss what the post-war world would look like. Stalin agreed that the Soviet Union would enter the fight against Japan after Germany’s surrender and, in return, the agreement was that the Soviets would take possession of the Kuril islands (Southern Sakhalin as well). The US did not disclose their plans about the nuclear bomb during the meeting (although it is known that there were Soviet spies inside the Manhattan Project).
The “Big Three” at Yalta, 9 February 1945. Photo: US government photographer, public domain, via Wikimedia Commons.
The Soviet Union declared war on Japan on Aug 8 1945. Nine days after the US dropped a second nuclear bomb on Japan (Nagasaki, Aug 9 1945), on Aug 18, the Soviets landed on Shumshu, the northernmost island, starting their occupation campaign of the archipelago. On the 23rd of August the Japanese garrison surrendered, following the general surrender of Japan (Aug 15). The southern islands fell between Aug 28 and Sep 3, and by Sep 5 the Soviets had fully occupied the archipelago. Japanese soldiers were taken prisoner (up to 60,000 across the Kurils) and the roughly 17,000 Japanese civilians were expelled from the islands between 1947 and 1949, most moving to Hokkaido.
Soviet administration
The Soviets moved quickly to impose their own culture, working to erase Japanese influence. Namely:
- Gave every island a Soviet name
- Started inhabiting them
- Destroyed Japanese-like houses to build Soviet-like houses
Up until today, the archipelago is mostly recognized as Russian.
Japanese claims
Japan still claims, until today, only the four southern islands called the “Northern Territories” (Iturup/Etorofu, Kunashir, Shikotan and the Habomai islands), where most Japanese lived and which are geographically closer to Japan. Its position is that they were never part of the Kurils it renounced.
The four islands Japan claims, northeast of Hokkaido. Public domain, via Wikimedia Commons.
Among the arguments is the San Francisco treaty, a treaty that marked the end of WWII, signed on September 8 1951. It was signed by 48 nations (plus Japan), not including the Soviet Union, even though they were present. This was an event that marked the Cold War as well. Japan signed the treaty renouncing all rights, title, and claim to the Kuril islands. However, it did not specify or assign sovereignty over to anyone.
Shigeru Yoshida signs the treaty, 8 September 1951. Public domain, via Wikimedia Commons.
So, since the Soviet Union did not sign, they weren’t obliged to follow it. Hence, from their perspective, they were able to keep the Kuril islands. This created a clear legal gap, which is where most Japanese claims come from.
In the 1956 Japan-USSR Joint Declaration the Soviets agreed to hand over Shikotan and the Habomai islands once a peace treaty was signed. No peace treaty has followed.
Modern days
A visa-free program between Russia and Japan was agreed in 1991 (Oct 14) and started in April 1992, so that displaced Japanese could visit their birthplaces and pay respect to the loved ones buried there.
More recently, Russia withdrew from this program in March 2022, following their invasion of Ukraine and the sanctions imposed by Japan. On August 13 2026 president Vladimir Putin made his first visit to the islands, to Iturup, amid strained relations over the Ukraine war. Japan’s prime minister Sanae Takaichi said that the visit was “absolutely unacceptable”.
South Sakhalin
South Sakhalin (Karafuto) was invaded a few days earlier, Aug 11-25 1945, and it was bloodier: about 600-1,200 Soviets and 700-2,000 Japanese soldiers died, plus at least 2,400 civilians when Soviet submarines sank two refugee ships on Aug 22. Unlike the Kurils, Japan makes no claim to it today.