The Battle of Shumshu, the Soviet invasion of Shumshu in the Kuril Islands, was the first stage of the Soviet Union's Invasion of the Kuril Islands in August–September 1945 during World War II. It took place from 18 to 23 August 1945, and was the only major battle of the Soviet campaign in the Kuril Islands and arguably the very last battle of World War II.
Background The Soviet Union and Japan maintained neutrality toward each other after signing the Soviet–Japanese Neutrality Pact on 13 April 1941, although the two countries were allied with each other's World War II enemies from 1941 until the conclusion of the war in 1945.Russell, Richard A., Project Hula: Secret Soviet-American Cooperation in the War Against Japan, Washington, D.C.: Naval Historical Center, 1997, , pp. 3–4. The Soviet Union turned down Allied requests for any actions which might provoke Japan, but discussed plans to base American aircraft on Soviet territory for operations against Japan after the Soviet Union had declared war on Japan.
Joseph Stalin said that the Soviet entry into the war against Japan would not be possible until after a three-month period following Germany's defeat,Russell, Richard A., Project Hula: Secret Soviet-American Cooperation in the War Against Japan, Washington, D.C.: Naval Historical Center, 1997, , pp. 4–8. per an assurance he offered to the United States Ambassador to the Soviet Union, W. Averell Harriman, at an October 1944 meeting. Stalin further stipulated as part of the agreement that it would include the Allies providing substantial assistance to the Soviet Union in building up its armed forces and military supplies in East Asia and the Pacific in advance of any Soviet operations against Japan. The United States soon began the work of meeting the Soviet requirements outside of and in addition to annual Lend-Lease allotments of aid to the Soviets,Russell, Richard A., Project Hula: Secret Soviet-American Cooperation in the War Against Japan, Washington, D.C.: Naval Historical Center, 1997, , p. 8. including the transfer of a dozen types of ships and aircraft from the United States to the Soviet armed forces. In the spring and summer of 1945, the United States secretly transferred 149 ships and craft – mostly escort vessels, landing craft, and minesweepers – to the Red Fleet at Cold Bay in the Territory of Alaska in Project Hula. Even so, cooperation between the Soviets and Americans was minimal and in August 1945 the Soviets did not have the capability to mount a major sea-borne invasion of Japanese-held territory.
As Stalin had promised, the Soviet Union declared war against Japan on 8 August 1945, exactly three months after the capitulation of Germany, and began an offensive against Japanese forces in Northeast Asia the next day. During August, Soviet forces attacked Japanese forces in the puppet state of Manchukuo in Manchuria, in the Japanese province of Karafuto on the southern half of Sakhalin Island, and the northern half of Korea, a Japanese possession at the time. Another Soviet goal during the offensive was the occupation of the Kuril Islands.
Shumshu is located at the northernmost part of the Kuril Islands and to the northeast, it faces Cape Lopatka on the Kamchatka Peninsula, separated by the Chishima Strait (Russia's "First Kuril Strait"). To the south, there is the Horomushiro Strait (Russia's "Second Kuril Strait") which separates it from Horomushiro Island. The area covers 230 square kilometers, with gently rolling hills at about 200 meters above sea level, consisting of marshlands and grasslands. It is surrounded by the Sea of Okhotsk and the Pacific Ocean. Even in summer, the temperature hovers around 15 °C, and dense fog often covers the area. In winter, temperatures drop to −15 °C, accompanied by blizzards.
In the secret agreement made during the Yalta Conference in February 1945, the Soviet Union (USSR) was to enter the war against Japan. In return, after the war, southern Sakhalin (South Sakhalin) and territories south of the 50th parallel north were to be ceded to the Soviet Union, and the Kuril Islands were to be handed over. However, in the notification sent by US President Harry S. Truman to Soviet Premier Joseph Stalin on 15 August, regarding the division of the Japanese military's surrender responsibilities, the Kuril Islands were not included as part of the Soviet zone. As a result, the Soviet side demanded that the Kuril Islands and the northeastern part of Hokkaido (the area north of the "Hokkaido Stalin Line" or "Rukushin Wall," which connects Kushiro and Rumoi) be included in the Soviet-controlled area. The United States, in its response on the 17th, rejected the northeastern part of Hokkaido but agreed to the inclusion of the Kuril Islands.中山117頁。中山200頁。ただし、北海道については拒否した。
Stalin argued that his right to control half of Hokkaido was a retaliation for the Siberian Intervention, and sought to seize the eastern part of Hokkaido through a rapid conquest of the Kuril Islands and Sakhalin. According to the "War History Series", the Soviet Union rushed to establish control over the Kuril Islands because the United States had requested the construction of airfields in the region, making it necessary for the Soviets to solidify their dominance there. In fact, after the ceasefire in Sakhalin on August 22, Stalin informed Truman that he would abandon the claim to Hokkaido, but negotiations regarding airfield construction continued with the United States over the Kuril Islands. On the 23rd, Nikolai Slavin, head of the Soviet General Staff, inquired through US Army Brigadier General John R. Deane, who was stationed in Moscow, to the US military command in Manila, asking, "Was it the American army that landed on Shumshu Island?" The US side replied that it was not the American army but the Soviet army. This exchange is documented in the telegram preserved at the MacArthur Memorial. Additionally, Brigadier General Deane mentioned in his memoir, Strange Alliance: The Story of Our Efforts to Cooperate with Russia During the War, that the Soviets suspected that the US had occupied the Kuril Islands. If even the upper echelons of the Soviet General Staff were unaware of the operation to invade the Kuril Islands, the operation may have been a highly secret mission based on the Yalta secret agreement.産経新聞 令和6年7月30日付『占守島侵攻でソ連が混乱』
Preparations On 15 August 1945, the commander-in-chief of Soviet armed forces in the Soviet Far East, Marshal of the Soviet Union Aleksandr M. Vasilevsky, ordered the commander of the Red Army's Second Far Eastern Front, General Maksim A. Purkayev, and the commander of the Red Fleet's Pacific Ocean Fleet, Admiral Ivan S. Yumashev, to take the first step in the conquest of the Kuril Islands by occupying the islands of Shumshu and Paramushiro at the northern end of the archipelago, just off the southern tip of the Soviet Union's Kamchatka Peninsula. Soviet forces first were to take Shumshu, then Paramushiro; with these two islands under control, the rest of the island chain, which was only lightly held, would fall easily.Russell, Richard A., Project Hula: Secret Soviet-American Cooperation in the War Against Japan, Washington, D.C.: Naval Historical Center, 1997, , pp. 29–33.
Purkayev and Yumashev placed the commander of the Red Army's Kamchatka Defense Zone, General A. R. Gnechko, and the commander of the naval base at Petropavlovsk-Kamchatsky, Captain 1st Rank Dmitri G. Ponomarev, in charge of the Shumshu operation, with Gnechko in overall command. Gnechko and Pomomarev had orders to assemble an assault force from forces locally available on the Kamchatka Peninsula and land on Shumshu within 48 hours.
Forces
Japanese The Japanese side, under the command of General Kiyichiro Higuchi, who headed the 5th Area Army (a unit of the Imperial Japanese Army), had been fortifying Shumshu Island and Horomushiro Island in anticipation of a war against the United States. By 1945, with preparations for the decisive battle on the home islands and the defense of Hokkaido, troops were withdrawn from the southern Kuril Islands such as Etorofu Island. However, at the time of Japan's surrender, the 91st Division (which consisted of two brigades) was still stationed there. The division's soldiers were mostly survivors of the Nomonhan Incident and the Battle of Guadalcanal, and many had also participated in the Kiska Island evacuation operation, making them highly experienced. Furthermore, as the northern front had seen little combat, stocks of food and ammunition were relatively abundant. Elite forces from Manchuria, such as the 11th Tank Regiment, were also stationed there.
As for air power, even combining the Army Air Squadrons and the Imperial Japanese Navy Air Units, only eight outdated aircraft remained by 1945.
Even by 1945, the main adversary that Japan expected to fight was the United States, and there were no special provisions made for preparedness against the Soviet Union. The defensive preparations for the U.S. were simply repurposed for defense against the Soviet Union.中山68～69頁。 With a reduction in defensive strength, the deployment strategy shifted from a decisive battle focus to ensuring control of critical zones, with particular emphasis on blocking passage through the Horomushiro Strait. As a result, in May, the Japanese Army concentrated its forces in the southern part of Horomushiro Island, particularly near Kashiwabara, which faced the Horomushiro Strait. On Shumshu Island, four battalions were concentrated in the southern part, while only one infantry battalion was assigned to the landing area at Takeda Beach as part of a guerrilla warfare mission. In the two beaches to the south, one infantry battalion was stationed on each, and an artillery battery of one company was stationed at the Kunichihama battery. The infantry battalions were tasked with a depth defense, primarily engaging in disruption of enemy forces rather than direct defense along the water's edge. Some key positions in the north, such as Kunichihama and Shimoyama, were to be held at all costs to prevent the enemy from advancing inland.
The Imperial Japanese Army's 91st Division garrisoned both Shumshu and nearby Paramushiro, with about 8,500 troops on Shumshu and 15,000 more troops on Paramushiro. The garrisons were able to reinforce one another if necessary. The Japanese fielded 77 tanks. Against this force, Gnechko was able to field two reinforced Soviet Army rifle divisions and a Soviet Naval Infantry battalion with a combined total of 8,824 officers and men and a naval task force of 64 small ships and craft to carry them to Shumshu. The Soviets had no tanks and no major warships to commit to the operation, but enjoyed an advantage in artillery and mortars.Russell, Richard A., Project Hula: Secret Soviet-American Cooperation in the War Against Japan, Washington, D.C.: Naval Historical Center, 1997, , p. 30.
The Imperial Japanese Navy had placed a special naval base force in the Kuril Islands, but similarly to the army, it moved its main forces to Hokkaido and disbanded, leaving behind only the 51st and 52nd security units stationed in the southern bases.