SAPPORO –

On the early morning of Aug. 22, 1945 — a week after the Pacific War ended on Aug.15 — three Japanese ships carrying Japanese evacuees from Soviet-invaded Sakhalin to Hokkaido were attacked and sunk by Soviet submarines near the port city of Rumoi, with a loss of over 1,700 lives.

Each year, the city commemorates the tragedy with a memorial ceremony at a cenotaph erected in 1962 dedicated to the victims of what became known as the Three Ships Incident. It was one of the final brutal acts of what remains the most devastating war in human history.

On the 80th anniversary of the tragedy, Rumoi officials are unsure how many survivors are still alive. But they said this year’s message will be to remind the world that those who were killed were largely women, children and noncombatants, and that the attacks were completely unjustified.

The attack by Soviet forces near Rumoi was also significant because of one of history’s greatest “what if” questions.

On. Aug. 8, 1945, the Soviet Union had declared war on Japan, one of the key factors that led to Japan’s surrender on Aug. 15. While the United States and other Allied nations halted combat operations after Japan’s surrender, the Soviet Union continued its military actions. Seeking to expand its influence in East Asia, Soviet leader Josef Stalin ordered Soviet forces to continue advancing and seize as much Japanese territory as possible.

Between Aug. 28 and Sept. 5, the Soviets seized the Northern Territories — the four islands of Etorofu, Kunashiri, Shikotan and Habomai — which had a population of 17,200 Japanese residents.

But declassified cables between U.S. President Harry Truman and Stalin later revealed that the Soviets had advanced plans to invade the island of Hokkaido as well, and occupy half of it while the U.S.-led forces would occupy the other half.

If that had happened, Rumoi would have found itself on the very border of a new Cold War in Asia.

On Aug. 15, shortly after Japan agreed to end the war, Truman issued an order to Douglas MacArthur, Supreme Commander for the Allied Powers in Japan, directing that Japanese forces on the Kuril Islands should surrender to the Soviet Union.

The following day, the Soviet Embassy in Washington received a message from Stalin with an additional demand, which was passed off to Truman.

“Include the northern half of the island of Hokkaido into the region of surrender by Japanese armed forces to Soviet forces. The demarcation line between the northern and southern halves of the island 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 Rumoi on the western coast of the island, including the said towns in the northern half of the island,” the cable read.

Stalin’s proposal would have led to all areas south of the line — including Sapporo, Otaru, Chitose, Niseko, Yoichi, and the ports of Tomakomai and Hakodate — coming under the control of the Allied Powers. The Shiretoko Peninsula and the far eastern port of Nemuro would have been under Soviet control.

The Soviet Union was, in fact, already preparing to invade Hokkaido. On Aug. 19, the commander of the Pacific Ocean Fleet sent a report outlining the operation to his superiors.

The plan called for the landing of Soviet rifle divisions in Rumoi as well as sending another division to the Kuril Islands on the eastern side. Soviet aircraft from a naval base in the Russian Far East were to support the invasion, and four submarines would seek out and destroy Japanese military vessels in the Tsugaru Strait and the La Perouse Strait, which separates Sakhalin and Hokkaido.

“The main forces of the rifle division are transported on 6 transport ships (under) the protection of four frigates, 4 trawlers and 4 large hunters. The first dash (group) departs with the calculation of being at the place of landing — the port of Rumoi — two hours ahead of the arrival of the main forces,” the cable stated.

But that same day, the Soviet Foreign Minister received a top secret message from the U.S. ambassador in Moscow. It contained Truman’s response to Stalin’s Aug. 16 request to include northern Hokkaido in the Soviet occupation.

“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, Hokkaido, Honshu, Shikoku, and Kyushu, to General MacArthur,” Truman said.

Between Aug.19 and Aug. 23, the Soviet Union continued to prepare for an invasion of Hokkaido. But on Aug. 23, the day after the three ships carrying Japanese evacuees were sunk near Rumoi, Stalin sent a formal reply via the Soviet Embassy in Washington to Truman regarding the U.S. president’s insistence that all Japanese forces on Hokkaido would surrender exclusively to MacArthur’s command.

“I understand the content of your message in the sense that you refuse to satisfy the request of the Soviet Union about including the northern half of the i(sland) of Hokkaido into the region of surrender of Japanese armed forces to Soviet forces. I must say that I and my colleagues did not expect such an answer from you,” Stalin replied.

As history would show, Soviet forces ultimately did not invade Hokkaido. Instead, the U.S. Army units arrived in Hakodate on Oct. 4, 1945, to begin the occupation of the island, while Soviet forces maintained control over the Northern Territories.

The reasons Stalin did not invade continue to be debated by historians. One is that the Soviets had already invaded Manchuria, then controlled by the Japanese army, on Aug. 9 — the day after declaring war on Japan — and determined that a second invasion of Hokkaido would be too difficult logistically at that point.

Hokkaido’s location put it on the front lines of the Cold War between the U.S. and the Soviet Union during that period. The Japanese Ground Self-Defense Force replaced U.S. troops as the island’s defenders, and until the Soviet Union was dissolved at the end of 1991, concerns about a Soviet invasion never went away entirely.

While many older Hokkaido residents have heard of the Soviet plan to occupy Hokkaido, younger generations appear to have fewer ways to learn about what might have happened. In Rumoi, officials say, there is no museum dedicated to the Soviet’s Hokkaido occupation plans, although some Rumoi area schools teach the tragedy of the three ships.

Eighty years after the end of the Pacific War, Japan and Russia have yet to sign a formal peace treaty, and Russian forces continue to occupy the Northern Territories — an enduring reminder that while Hokkaido was never invaded, the legacy of Soviet-era tensions still lingers.