Soviet–Japanese War

• 1. Introduction

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  The Soviet-Japanese War began at one minute past midnight Trans-Baikal time on the 9th of August 1945, when three Red Army fronts crossed into Manchuria simultaneously from the east, west, and north. It lasted less than a month. Yet in that span, the Soviet Union dismantled Japan's largest land army, seized territories across a region the size of Western Europe, and helped shatter the political deadlock that had kept Japan from surrendering. What made this blitz so decisive? Why had Japan's leaders not seen it coming? And whose decision was it, really, that ended the Second World War in the Pacific?

• 2. Years of Secret Preparation

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  At the Tehran Conference in November 1943, Joseph Stalin made a private promise to Winston Churchill and Franklin Roosevelt: the Soviet Union would enter the war against Japan once Germany was defeated. At that point, Stalin faced a genuine strategic bind. He wanted gains in the Far East, but he was also determined to avoid fighting on two fronts at once. The only way to have both was to wait for Germany to fall first.

  The Soviet-Japanese Neutrality Pact, signed in April 1941, had given Moscow breathing room. It freed Soviet forces from border skirmishes with Japan and let them focus entirely on the German invasion. For Tokyo, the pact did the same: Japan could push south into Asia and the Pacific without worrying about its exposed rear in Manchuria.

  By early 1945, however, the pact was becoming a diplomatic fiction. On the 5th of April 1945, Soviet foreign minister Vyacheslav Molotov informed Japan that the Soviet Union would not renew the treaty. The Soviets then immediately reassured Japan that the treaty would remain in force for another twelve months. It was a deliberate deception. Behind the scenes, the Soviets had already been moving 90 divisions into the Far East, many of them crossing Siberia in their vehicles to avoid straining the Trans-Siberian Railway's limited freight capacity.

  At the Yalta Conference in February 1945, Stalin formalized his commitment. He agreed to enter the Pacific War within two or three months of the German surrender, and Roosevelt agreed to support Soviet territorial ambitions in return. Germany surrendered on the 9th of May 1945, which set an internal deadline: Stalin had to be at war with Japan by the 9th of August 1945 to honor the Yalta Agreement.

• 3. Japan's Fatal Miscalculation

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  Japan's military intelligence had been watching the Trans-Siberian Railway closely and tracking Soviet activity along the east Manchurian border. Based on what they observed, they concluded the Soviets would not have sufficient forces in place before the end of August, and that a serious attack was most likely in the autumn of 1945 or even the spring of 1946.

  This estimate was wrong on nearly every count. The Soviets had concealed their buildup of 90 divisions, and many of those units had crossed Siberia by road rather than rail precisely to avoid detection. The Japanese had also prepared for an invasion from the east. They had not seriously planned for an assault from the west through the Greater Khingan mountain range, which they considered impassable.

  Making things worse, the Kwantung Army had been quietly hollowed out. Over the previous three years, its elite troops and heavy equipment had been stripped away and sent to the Pacific fronts. Second-rate units were raised to replace them, and overall ammunition stockpiles were only sufficient to meet the needs of 13 divisions for three months, even though 24 divisions were then stationed in Manchuria. The Kwantung Army had effectively been reduced to a light infantry force with no realistic ability to hold ground against a coordinated armored offensive.

  In June 1945, the Cabinet of Admiral Baron Suzuki, which had taken office in April, approached the Soviets with an offer: in exchange for Soviet help in brokering a conditional peace with the Western Allies, Japan would make very attractive territorial concessions. Stalin expressed interest. Japan waited for a response that never came, holding on to hopes of a negotiated exit from the war right up to the moment the invasion began.

• 4. The Invasion Itself

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  At 5 p.m. Moscow time on the 8th of August 1945, Soviet foreign minister Molotov summoned Japanese ambassador Naotake Sato to the Kremlin and delivered the declaration of war. Just over an hour later, at midnight Trans-Baikal time, Soviet forces attacked simultaneously on three fronts.

  Marshal Rodion Malinovsky's Transbaikal Front drove from the west, crossing the Inner Mongolian desert and the Greater Khingan mountains in a drive that the Japanese had not anticipated. Marshal Kirill Meretskov's 1st Far East Front attacked from the east, crossing the Ussuri River and pressing toward Mudanjiang. General Purkayev's 2nd Far East Front pushed from the north toward Harbin and Qiqihar. The combined Soviet force totaled 89 divisions with 1.5 million men, 3,704 tanks, 1,852 self-propelled guns, 85,819 vehicles, and 3,721 aircraft.

  The Kwantung Army commanders were away from their posts for the first 18 hours of the conflict, involved in a planning exercise at the time of the attack. Communication with forward units was lost almost immediately. Soviet airborne units were used to seize airfields and city centers ahead of the land forces, and also to ferry fuel to armored columns that had outrun their supply lines advancing through terrain the Japanese had assumed no large force could cross.

  Japanese resistance was fierce in places. At Hailar, defenders tied down Soviet forces with sustained fighting. In the east, Japanese defenders fought hard around Mudanjiang. The Japanese also used 37mm and 47mm anti-tank guns against Soviet armor, but these proved ineffective against modern Soviet tanks, and Japanese troops resorted to soldiers strapping themselves with grenades and explosives and attacking Soviet tanks on foot.

  In Inner Mongolia, the dynamic was different. Soviet forces there were largely Mongolian troops from Outer Mongolia. Japanese forces abandoned their city stronghold of Kalgan and fled south without serious resistance.

• 5. Korea and the Territories

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  The 1st Far East Front had a secondary objective beyond encircling the Kwantung Army: to prevent Japanese forces from escaping south into Korea, and then to invade the Korean Peninsula up to the 38th parallel. This assignment would shape the region for decades.

  On the 10th of August, the US government proposed to the Soviet government that they divide the occupation of Korea at the 38th parallel north. American officials were surprised when the Soviets accepted. Soviet troops could move freely by rail and faced nothing that could stop them from taking the entire peninsula.

  Soviet amphibious landings in northern Korea began by the 14th of August. On the 16th of August, Soviet forces landed at Wonsan. On the 24th of August, the Red Army entered Pyongyang and established a military government over Korea north of the 38th parallel. American forces did not land at Incheon until the 8th of September.

  Further north, the South Sakhalin Operation ran from the 11th to the 25th of August, and the Kuril Landing Operation ran from the 18th of August to the 1st of September. In Karafuto and the Chishima Islands, the Soviet military presence constituted an immediate and decisive assertion of sovereignty over territories Japan had held for decades. South Sakhalin was a direct reversal of the outcome of the Russo-Japanese War, which Russia had lost in 1905. As agreed at Yalta, the Soviets were entitled to annex South Sakhalin and the Kuril Islands; those territories remain under Russian administration today as the Sea of Okhotsk became a Soviet inland sea.

  The division of Korea into two occupation zones, established in days by military convenience, became the precursor to the Korean War five years later.

• 6. Who Ended the War

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  The debate over what finally broke Japan's will to fight is one of the most contested questions in modern military history. American historian Richard B. Frank, writing in the "Sixty Years after Hiroshima" issue of The Weekly Standard, laid out the competing schools of thought: the traditionalist view that the atomic bombings caused Japan's surrender, an alternative that Japan's leaders had already concluded their situation was hopeless, and a third position focused on the Soviet entry into the war.

  Historian Tsuyoshi Hasegawa has argued that the Soviet declaration of war was more decisive than the atomic bombings. His reasoning is structural: Japan's defense strategy for the home islands was designed to repel an Allied invasion from the south. It left virtually no forces to counter a Soviet threat from the north. When Stalin declared war on the 8th of August, he did not just add a new enemy. He destroyed the last diplomatic option Japan had. Japan could no longer use the Soviet Union as a neutral mediator to negotiate a conditional peace with the Allies. Hasegawa called this a "strategic bankruptcy" for Japan, and he argued that it forced the surrender message of the 15th of August 1945.

  Ward Hayes Wilson has gone further, arguing the Soviet declaration was the sole cause. He points to a meeting of Japan's Supreme Council in June 1945, at which the council concluded that maintaining Soviet neutrality would "determine the fate of the Empire."

  Most historians, including Hasegawa, acknowledge that the surrender was not caused by any single factor. The Manchurian Strategic Offensive Operation, combined with the atomic bombings, broke the political deadlock among Japan's leaders and ended the argument over terms. The "Big Six," the powerful military leaders who had kept Japan from accepting any surrender terms, could no longer hold their position once the northern front collapsed and Soviet mediation vanished as a hope.

  The civilian leaders had actually been seeking an exit from the war since 1943, calculating that Japan did not have the industrial capacity to fight the United States, China, and the British Empire simultaneously. The August crisis gave them the ground they needed to move.

• 7. The Occupation's Human Cost

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  For the more than one million Japanese residents of Manchukuo, the Soviet arrival meant the abrupt end of the world they had built. Japanese military occupants were captured and transferred to Siberia to perform forced labor, where many died from the cold. Others were held in Siberian prisons for up to 20 years.

  Japanese colonists who had been born in Manchukuo were now stateless. The Manchurian population wanted them gone. Some made their way to the Japanese home islands, where they were also treated as foreigners. Japanese evacuees who reached Beijing carried accounts of Soviet mistreatment, and those stories spread panic among Japanese civilians.

  Beyond the human toll, Soviet forces systematically stripped Manchuria's industrial infrastructure before withdrawing. Almost all of the portable parts of the considerable Japanese-built industrial base were dismantled and relocated to the Soviet Union, framed officially as restoration of Soviet industry damaged in the war against Germany. Equipment that could not be moved was disabled or destroyed; the Soviets had no interest in Manchuria becoming an economic competitor, particularly to underdeveloped Soviet territories in the Far East.

  What remained of Manchuria's industrial capacity became the foundation for Mao Zedong's forces in the Chinese Civil War. With Soviet backing, the Communist Chinese used Manchuria as their main base of operations and proved victorious in the four years following the war. After the People's Republic of China was established in 1949, the USSR began providing economic assistance to the new government, and the bulk of that aid went into rebuilding Manchuria's industrial base. The territories on the Asian mainland that the Soviets had occupied were transferred to full Chinese control in 1955.