U.S. President Harry Truman (L) put the brakes on Soviet dictator Joseph Stalin’s plan to invade Japan.
Updated: Date
Published: MAY 2024

Little-known August 1945 incident could have changed course of history

Soviets were within 48 hours of invading Japan and dividing it in two à la Vietnam and Korea

Japan is today a vital partner, and increasingly so, in the effort by democratic-style states to counter China’s aggressive assertiveness. But it could have turned out differently. Much differently.

In September 1941, reportedly alerted by its Tokyo-based spy Richard Sorge that Japan had no imminent intention of attacking the Soviet Union, Moscow felt free to shift massive forces from its Far East Command to the campaign against Nazi Germany. Its focus would remain on Berlin until the closing weeks of the Second World War.

Soviet leader Joseph Stalin had agreed at the 1943 Tehran Conference to join the war against Japan once the Nazi threat was defeated, and he vowed at the 1945 Yalta Conference do so within three months of Berlin’s surrender. True to his word, the Soviet Union attacked the Japanese puppet state of Manchukuo (in China’s Manchuria region) on 9 August after declaring war against Japan a day earlier.

With the Imperial Japanese Army in shambles, Soviet forces swept into Manchukuo and advanced swiftly on several other fronts. These included northern Korea, South Sakhalin and the Kuril Islands chain. An estimated 500,000 to 750,000 Japanese nationals were subsequently interned in Soviet labour camps, many for decades, and some 55,000 are thought to have perished in captivity.

Stalin had intended to continue this campaign with an invasion of Hokkaido, the northern-most island of the Japanese mainland. But he demurred two days before the scheduled attack on 24 August, leaving Japan proper to the Americans.

Some suggest that Stalin’s change of heart was due to Washington’s revelation some two weeks earlier of its nuclear power. The U.S. had until then kept its nuclear programme a closely guarded secret, but Soviet intelligence had long alerted Moscow to its progress and Stalin was far from cowed. “Not atomic bombs, but armies decide about the war,” he said confidently to Polish Communist leader Wladyslaw Gomulka in November 1945.

Stalin wrote to U.S. President Harry Truman on 16 August seeking his assent to the planned Soviet invasion of Hokkaido. This reads in part: “Include the northern half of the island of Hokkaido, which adjoins in the north the Laperouse Strait [La Perouse Strait – ed.], located between Karafouto [Karafuto – ed.] and Hokkaido, into the region of surrender by Japanese forces to Soviet forces. The demarcation line between the northern and southern halves of Hokkaido is to be drawn along the line extending from the town of Kushiro on the eastern coast of the island until the town of Rumoe [Rumoi – ed.] on the western coast of the island, including the said towns in the northern half of the island.”

Give ‘em hell, Harry!

Two days later, emboldened by events at Hiroshima and Nagasaki, Truman turned him down. “Regarding your suggestion as to the surrender of Japanese forces on the island (of) Hokkaido to Soviet forces, it is my intention and arrangements have been made for the surrender of Japanese forces on all the islands of Japan proper (...) to General MacArthur,” he responded. The U.S. president accepted Moscow’s seizure of the Kuril Islands elsewhere in that same letter, but asked for U.S. air base rights there – a proposal that the Soviet Union ignored.

President Harry Truman accepted the Soviet seizure of Japan’s Kuril Islands in 1945.

Writing several years ago in U.S.-based Foreign Policy magazine, Sergey Radchenko, a Soviet-born British historian who is a professor at John Hopkins University, argued that Stalin accepted this decision because he had a more pressing agenda.

“Even a cynical realist like Stalin wanted not so much geopolitical gains as U.S. recognition of his sphere of interests. Attractive for geopolitical reasons, Hokkaido was not part of the deal agreed upon at Yalta in February 1945. Stalin knew that by violating this agreement he risked undermining Soviet gains in the Far East, including possession of southern Sakhalin and the Kuril Islands,” Radchenko wrote. “Stalin wanted Soviet-U.S. cooperation to continue, with each country respecting the other’s legitimate claims.”

Stalin later came to regret his acquiescence, which he formalised with a military order on 22 August. That was just two days before the planned assault. “In August 1945...he still saw Truman as a partner in the postwar management of the world. That feeling did not last,” Radchenko noted.

The Soviet invasion plan for Hokkaido was drawn up by Admiral Ivan Yumashev, Moscow’s military commander in the Far East, and initially centred on seizing the port of Rumoi. The beachhead was to be established by one naval infantry regiment and one rifle regiment, followed two hours later by two rifle divisions with significant air and naval support.1

Communist ideology had meanwhile been established in the country since the Japanese Communist Party was founded in 1922 under Moscow’s firm control, though operations became clandestine when it was immediately outlawed. The party nevertheless attracted over 2.1 million votes, or 3.8 percent of the ballots cast, on being permitted to contest Japan’s first postwar election in 1946.

These elements – control over territory, an active Communist Party structure and some degree of popular support – suggest that Japan came within two days of being split in the manner of Korea and Vietnam. And what a different Japan, what a widely different geostrategic environment, this would have meant.      

These events remain significant to this day, beyond their historical interest.

It is often noted that belligerents involved in the 1950-53 Korean War – Democratic People’s Republic of Korea and China on the one side, the U.S.-led United Nations Command on the other – remain technically at war in the absence of a peace treaty, the conflict having been indefinitely suspended by an armistice agreement. But the same holds true for the Soviet-Japanese War, with the central issue to its final resolution centred on competing claims to part of the Kuril Islands chain.

Moscow refused to sign the 1951 Treaty of San Francisco, the peace agreement that formally ended the Second World War, due to Cold War factors. Instead, it forged a separate end to hostilities five years later with the 1956 Soviet-Japanese Joint Declaration. Though this has legal status to end hostilities, it is still simply a prelude to a peace treaty whose details have been the subject of sporadic bickering ever since.

The central dispute blocking agreement involves four small islands north of Hokkaido: Kunashiri, Etorofu, Shikotan and the Habomai Rocks. In Japan these are known collectively as the Northern Territories.

Map showing coastline of Russia and nearby islands of Japan including Hokkaido, Kunashiri, Etorofu, Shikotan, and Habomai Rocks.

Tokyo’s position is that the Joint Declaration has Shikotan and the Hobamai Rocks being ceded to Japan after a peace treaty is concluded, while sovereignty over the other two islands must be decided through negotiations leading to a peace deal. Moscow’s position, as stated in 2006 by the Putin administration, is that Shikotan and the Habomai Rocks will be handed over only after Japan renounces its claim to the other two islands. And so the situation remains.

This seemingly minor dispute evokes sharp nationalist sentiment in both countries, but there are practical considerations beyond the territory involved.

“The level of confidence, of cooperation, of trust between both governments will increase dramatically if we can resolve the (Northern Territories) issue,” a Japanese Ministry of Foreign Affairs official told this writer in 2010. “In July 2008 the two leaders met and both sides agreed that the fact there exists no peace treaty between Japan and Russia is not conducive to the enhancement of relations.

“I think the Russian side understands the importance of strategically upgrading the relationship with Japan to a higher level. And I think they understand that to make this happen they have to resolve the issue of the islands.”

According to a report in the Japan Times, “Japanese Prime Minister Shinzo Abe and Russian President Vladimir Putin agreed in a 2016 summit to conduct joint economic activity on and around the four islands under a special framework that will not undermine their respective legal positions on the sovereignty of the islands”. This has so far led to no real progress, and Russian Foreign Minister Sergei Lavrov has stated that Japan’s strengthening of its missile shield in conjunction with the U.S. could scuttle any further steps to reaching a peace treaty deal.

Under a “two-plus-two” security dialogue regime that brings together their respective foreign and defence ministers, Japan was in 2017 the first Western-aligned country to resume such a process with Russia since the latter’s 2014 seizure of Crimea. But whatever potential this might have offered was shattered by Moscow’s 2022 invasion of Ukraine, which saw Tokyo align firmly with Kyiv

Its support of Ukraine has so far included economic sanctions against Russia, among them revoking its most favoured nation status, and at least $12.1 billion U.S. in financial and humanitarian aid. Beyond that, Tokyo earlier this year pledged a further $105 million U.S. to Kyiv for demining and a range of reconstruction projects while also announcing a new government trade office in the Ukrainian capital.

Russia, for its part, has come to see Japan as an “unfriendly” country. And Moscow’s growing military cooperation with Beijing in the context of its war in Ukraine is meanwhile emerging as a potential security threat to Japan.

Together with its American security partner (and several other countries), Japan is increasingly wary of China’s ambitions amid the expansion of Beijing’s economic and military power. Some see this as having prompted a recent buildup of Tokyo’s military posture, but this is an evolutionary process that began to germinate nearly 50 years ago.

The 1947 Constitution of Japan, which remains in place, was written by Washington and aimed through  Article 9 to demilitarize the country. This was soon neutralised by Cold War contingencies, with Japan’s Self Defence Force (SDF) established in 1954 and a 1960 military alliance treaty with the U.S. focused on a joint commitment to defend Japanese territory.

The SDF began to unshackle itself from the U.S. in 1976 with its inaugural defence policy paper, but the end of the Cold War in the early 1990s dislodged the foundation of Japan’s security posture. A cautious post-Cold War rethinking produced a new strategic policy through Japan’s 1995 National Defence Program Guidelines (NDPG), which included a new role for the SDF in contributing to a more stable regional and global security environment. 

This broad commitment has since begun to find substance.

The 1995 NDPG called for an expanded security relationship with the U.S., which is seen by Tokyo as a stabilising force, and formalized new roles for the SDF in disaster relief and peacekeeping operations. It also opened the door to enhanced security cooperation with a wider range of countries.

Japan’s updated 2010 NDPG expands on the vision introduced 15 years earlier. It speaks of “facilitating cooperation with (the U.S.) and countries in the Asia-Pacific, and pursuing multilayer security cooperation with the international community in a consolidated manner”.  The approach has been incremental.

Japan’s postwar security posture was at first strictly limited to territorial defence. But at least since 1995, Tokyo has begun to accept that defending Japan cannot be limited to meeting threats, or potential threats, at its shoreline. That there exists a wider context demanding attention.

It’s fair to guess, though, that things would have come out very differently had the Soviet Union invaded Hokkaido on 24 August 1945 to establish there the People’s Republic of Japan.


1. The Soviet Union’s operational plan to invade Hokkaido, in both the Russian original and in English-language translation, can be found in the Wilson Center Digital Archive, which contains declassified historical materials about wars and conflicts from archives around the world: The Wilson Center is maintained at the University of North Carolina at Chapel Hill and is connected to The Oxford University Press Handbook of Cender, War, and the Western World Since 1600.

© ROBERT KARNIOL. All Rights Reserved. Publication by 2012-2024.
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