Soviet–Japanese War (1945)

The Soviet-Japanese War of 1945 (Советско-японская война, lit. Soviet-Japanese War), began on August 9, 1945, with the Soviet invasion of the Japanese puppet state of Manchukuo. The Soviets terminated Japanese control of Manchukuo, Mengjiang (inner Mongolia), northern Korea, southern Sakhalin, and the Kuril Islands. The rapid defeat of Japan's Kwantung Army was a significant factor in the Japanese surrender and the termination of World War II.

Summary
At the Tehran Conference (November 1943), Stalin agreed that the Soviet Union would enter the war against Japan once Nazi Germany was defeated. At the Yalta Conference (February 1945), Stalin agreed to Allied pleas to enter World War II's Pacific Theater within three months of the end of the war in Europe. The invasion began on August 8, 1945, precisely three months after the German surrender on May 8 (May 9, 0:43 Moscow time).

The commencement of the invasion fell between the atomic bombings of Hiroshima, on August 6, and Nagasaki, on August 9. Although Soviet leader Joseph Stalin had not been told much detail of the Western Allies' atomic bomb program by Allied governments, he was nonetheless well aware of its existence and purpose by means of Soviet intelligence sources. However, by virtue of the timing of the agreements at Tehran and Yalta, and the long term buildup of Soviet forces in the Far East since Tehran, it is clear that news of the attacks on the two cities played no major role in the timing of the Soviet invasion; the date of the invasion was foreshadowed by the Yalta agreement, the date of the German surrender, and the fact that on August 3, Marshal Vasilevsky reported to Stalin that, if necessary, he could attack on the morning of August 5. Furthermore, while Stalin could reasonably have concluded that an atomic bombing of Japan was imminent, it does not appear he was overly impressed with the atomic bomb's potential, certainly not so much so as to think it might compel a nation as averse to surrender as Japan into an earlier capitulation.

At 11pm Trans-Baikal time on August 8, 1945, Soviet foreign minister Molotov informed Japanese ambassador Sato that the Soviet Union had declared war on the Empire of Japan, and that from August 9 the Soviet Government would consider itself to be at war with Japan. At one minute past midnight Trans-Baikal time on August 9, 1945, the Soviets commenced their invasion simultaneously on three fronts to the east, west and north of Manchuria. The operation was subdivided into smaller operational and tactical parts: and subsequently
 * Khingan-Mukden Offensive Operation (August 9, 1945 - September 2, 1945)
 * Harbin-Kirin Offensive Operation (August 9, 1945 - September 2, 1945)
 * Sungari Offensive Operation (August 9, 1945 - September 2, 1945)
 * South Sakhalin Army Group Offensive Operation (August 11, 1945 - August 25, 1945)
 * Seisin Landing Operation (August 13, 1945 - August 16, 1945)
 * Kuril Landing Operation (August 18, 1945 - September 1, 1945)

Though the battle extended beyond the borders traditionally known as Manchuria — that is, the traditional lands of the Manchus — the coordinated and integrated invasions of Japan's northern territories has also been called the Battle of Manchuria. Since 1983, the operation has sometimes been called Operation August Storm, after American Army historian LTC David Glantz used this title for a paper on the subject. It has also been referred to by its Soviet name, the Manchurian Strategic Offensive Operation, however this name refers more to the Soviet invasion of Manchuria (1945) than to the whole war.

This offensive should not be confused with the Soviet-Japanese Border Wars, (particularly the Battle of Khalkhin Gol/Nomonhan Incident of May–September 1939), that ended in Japan's defeat in 1939, and led to the Soviet–Japanese Neutrality Pact.

Background and buildup
The Russo-Japanese War of the early 20th century resulted in a Japanese victory and the Treaty of Portsmouth by which, in conjunction with other later events including the Mukden Incident and Japanese invasion of Manchuria in September 1931, Japan eventually gained control of Korea, Manchuria and Southern Sakhalin. In the late 1930s there were a number of Soviet-Japanese border incidents, the most significant being the Battle of Lake Khasan (Changkufeng Incident, July–August 1938) and the Battle of Khalkhin Gol (Nomonhan Incident, May–September 1939), which led to the Soviet–Japanese Neutrality Pact of April 1941. The Neutrality Pact freed up forces from the border incidents and enabled the Soviets to concentrate on their war with Germany, and the Japanese to concentrate on their southern expansion into Asia and the Pacific Ocean.

However, with success at Stalingrad, and the eventual defeat of Germany becoming increasingly certain, the Soviet attitude to Japan changed, both publicly, with Stalin making speeches denouncing Japan, and "privately", with the Soviets building up forces and supplies in the Far East. At the Tehran Conference (November 1943), amongst other things, Churchill, Roosevelt and Stalin agreed that the Soviet Union would enter the war against Japan once Nazi Germany was defeated. However, Stalin faced a dilemma - he wanted to avoid a two-front war at almost any cost yet the Soviet leader also wanted to extract gains in the Far East as well as Europe. The only way Stalin could make Far Eastern gains without a two-front war would be for Germany to capitulate before Japan.

Due to the Soviet-Japanese Neutrality Act, the Soviets made it policy to intern Allied aircrews who landed in Soviet territory following operations against Japan, although airmen held in the Soviet Union under such circumstances were usually allowed to "escape" after some period of time. Nevertheless, even before the defeat of Germany the Soviet buildup in the Far East steadily accelerated. By early 1945 it had become apparent to the Japanese that the Soviets were preparing to invade Manchuria, though they were unlikely to attack prior to Germany's defeat. In addition to their problems in the Pacific, the Japanese realised they needed to determine when and where a Soviet invasion would occur.

At the Yalta Conference (February 1945), amongst other things, Stalin secured from Roosevelt the promise of Stalin's Far Eastern territorial desires, in return agreeing to enter the Pacific war within two or three months of the defeat of Germany. By the middle of March 1945, things were not going well in the Pacific for the Japanese, and they withdrew their elite troops from Manchuria to support actions in the Pacific. Meanwhile the Soviets continued their Far Eastern buildup. The Soviets had decided that they did not wish to renew the Neutrality Pact. The terms of the Neutrality Pact required that 12 months before its expiry, the Soviets must advise the Japanese of this, so on 5 April 1945 they informed the Japanese that they did not wish to renew the treaty. This caused the Japanese considerable concern, but the Soviets went to great efforts to assure the Japanese that the treaty would still be in force for another twelve months, and that the Japanese had nothing to worry about.

On 9 May 1945 (Moscow time), Germany surrendered, meaning that if the Soviets were to honour the Yalta agreement, they would need to enter war with Japan by 9 August 1945. The situation continued to deteriorate for the Japanese, and they were now the only Axis power left in the war. They were keen to remain at peace with the Soviets and extend the Neutrality Pact, and they were also keen to achieve an end to the war. Continuously since Yalta they had repeatedly approached, or tried to approach, the Soviets in order to extend the neutrality pact, and to enlist the Soviets in negotiating peace with the allies. The Soviets did nothing to discourage these Japanese hopes, and drew the process out as long as possible (whilst continuing to prepare their invasion forces.) One of the roles of the Cabinet of Admiral Baron Suzuki, which took office in April 1945, was to try to secure any peace terms short of unconditional surrender. In late June they approached the Soviets, (the Neutrality Pact was still in place), inviting them to negotiate peace with the allies in support of Japan, providing them with specific proposals and in return they offered the Soviets very attractive territorial concessions. Stalin expressed interest, and the Japanese awaited the Soviet response. The Soviets continued to avoid providing a response. The Potsdam Conference was held from 16 July to 2 August 1945. On 24 July the Soviet Union recalled all embassy staff and families from Japan. On 26 July the conference produced the Potsdam Declaration whereby Churchill, Truman and Chiang Kai-shek (the Soviet Union was not at war with Japan) demanded the unconditional surrender of Japan. The Japanese continued to wait for the Soviet response, and avoided responding to the declaration.

The Japanese had been monitoring Trans-Siberian Railway traffic and Soviet activity to the east of Manchuria and in conjunction with the Soviet delaying tactics, this suggested to them that the Soviets would not be ready to invade east Manchuria before the end of August. They did not, however, have any real idea, and no confirming evidence, as to when or where any invasion would occur.

The Japanese were caught completely by surprise when the Soviets declared war an hour before midnight on 8 August 1945, and invaded simultaneously on three fronts just after midnight on 9 August.

Combatant forces

 * See Soviet invasion of Manchuria (1945) for the tactical details of the combatant forces and of the invasion.

Soviets
The Far East Command, under Marshal of the Soviet Union Aleksandr Vasilevsky, had a plan for the conquest of Manchuria that was simple but huge in scale, calling for a massive pincer movement over all of Manchuria. This pincer movement was to be performed by the Transbaikal Front from the west and by the 1st Far East Front from the east; the 2nd Far East Front was to attack the center of the pocket from the north. The only Soviet equivalent of a theater command that operated during the war (apart from the short-lived 1941 "Directions" in the west), Far East Command, consisted of three Red Army fronts.

The Transbaikal Front, under Marshal R. Y. Malinovsky, was to form the western half of the Soviet pincer movement, attacking across the Inner Mongolian desert and over the Greater Khingan mountains. These forces had the objective to secure Mukden (present day Shenyang), then meet troops of the 1st Far East Front at the Changchun area in south central Manchuria, and in doing so finish the double envelopment.
 * Western Front of Manchuria

The 1st Far East Front, under Marshal K. A. Meretskov, was to form the eastern half of the pincer movement. This attack involved striking towards Mudanjiang (or Mutanchiang), and once that city was captured, the force was to advance towards the cities of Jilin (or Kirin), Changchun and Harbin. Its final objective was to link up with forces of the Trans-Baikal Front at Changchun and Jilin (or Kirin) thus closing the double envelopment movement.
 * Eastern Front of Manchuria

As a secondary objective, the 1st Far East Front was to prevent Japanese forces from escaping to Korea, and then invade the Korean peninsula up to the 38th parallel, establishing in the process what later became North Korea.

The 2nd Far East Front, under General M. A. Purkayev, was in a supporting attack role. Its objectives were the cities of Harbin and Tsitsihar, and the prevention of an orderly withdrawal to the south by the Japanese forces.
 * Northern Front of Manchuria

Once troops from the 1st Far East Front and Trans-Baikal Front captured the city of Changchun, the 2nd Far East Front were to attack the Liaotung Peninsula and seize Port Arthur (present day Lüshun).

Each Front had "front units" attached directly to the Front instead of an army. The forces totaled 89 divisions with 1.5 million men, 3,704 tanks, 1,852 self propelled guns, 85,819 vehicles and 3,721 aircraft. Approximately one-third of its strength was in combat support and services. Its naval forces contained 12 major surface combatants, 78 submarines, numerous amphibious craft, and the Amur river flotilla, consisting of gunboats and numerous small craft. The Soviet plan incorporated all the experience in maneuver warfare that the Soviets had acquired fighting the Germans.

Japanese
The Kwantung Army of the Imperial Japanese Army, under General Otsuzo Yamada, was the major part of the Japanese occupation forces in Manchuria and Korea, and consisted of two Area Armies (the First Area Army (northeastern Manchukuo) and the Third Area Army (southwestern Manchukuo)), and three independent armies (responsible for northern Manchuria, North Korea, Mengjiang, South Sakhalin and the Kurils).

Each Area Army (Homen Gun, the equivalent of a Western "army") had headquarters units and units attached directly to the Area Army, in addition to the field armies (the equivalent of a Western corps). In addition to the Japanese, there was the forty-thousand-strong Manchukuo Defense Force, composed of eight under-strength, poorly equipped, poorly trained Manchukuoan divisions.

The Kwantung Army had over six hundred thousand men in twenty-five divisions (including two tank divisions) and six Independent Mixed Brigades. These contained over 1,215 armored vehicles (mostly armored cars and light tanks), 6,700 artillery pieces (mostly light), and 1,800 aircraft (mostly trainers and obsolete types; they only had 50 first line aircraft). The Imperial Japanese Navy contributed nothing to the defense of Manchuria, the occupation of which it had always opposed on strategic grounds.

On economic grounds, Manchuria was worth defending since it had the bulk of usable industry and raw materials outside of Japan and was still under Japanese control in 1945. However, the Japanese forces (Kwantung Army) were far below authorized strength; most of their heavy military equipment and all of their best military units had been transferred to the Pacific front over the previous three years. By 1945, the Kwantung Army contained a large number of raw recruits. As a result, the Kwantung Army had essentially been reduced to a light infantry counter-insurgency force with limited mobility and experience. On paper, the Japanese forces were no match for the highly mobile mechanized Red Army, with its vastly superior tanks, artillery, experience and tactics.

Compounding the problem, the Japanese military made many wrong assumptions and major mistakes, the two most significant being:
 * They wrongly assumed that any attack coming from the west would follow either the old railroad line to Hailar, or head into Solun from the eastern tip of Mongolia. The Soviets did attack along those routes, but their main attack from the west went through the supposedly impassable Greater Khingan range south of Solun and into the center of Manchuria.
 * Japanese military intelligence failed to determine the nature, location and scale of the Soviet buildup in the Far East. Based on initial underestimates of Soviet strength, and the monitoring of Soviet traffic on the Trans-Siberian railway, they believed the Soviets would not have sufficient forces in place before the end of August, and that an attack was most likely in the autumn of 1945 or in the spring of 1946.

Due to the withdrawal of the Kwantung Army's elite forces for redeployment into the Pacific Theatre, new operational plans for the defence of Manchuria against a seemingly inevitable Soviet attack were made by the Japanese in the summer of 1945. These called for the redeployment of the majority of forces from the border areas; the borders were to be held lightly and delaying actions fought while the main force was to hold the southeastern corner in strength (so defending Korea from attack).

Further, they had only observed Soviet activity on the Trans-Siberian railway and along the east Manchurian front, and so were preparing for an invasion from the east. They believed that when an attack occurred from the west, the redeployed forces would be able to deal with it.

However, although this redeployment had been initiated, it was not due to be completed until September, and hence the Kwantung Army were in the middle of redeployment when the Soviets launched their attack simultaneously on all three fronts.

Campaign
The operation was carried out as a classic double pincer movement over an area the size of Western Europe. In the western pincer, the Red Army advanced over the deserts and mountains from Mongolia, far from their resupply railways. This confounded the Japanese military analysis of Soviet logistics, and the defenders were caught by surprise in unfortified positions. The Kwantung Army commanders were involved in a planning exercise at the time of the invasion, and were away from their forces for the first eighteen hours of conflict. Communication infrastructure was poor, and communication was lost with forward units very early on. However, the Kwantung Army had a formidable reputation as fierce and relentless fighters, and even though understrength and unprepared, put up strong resistance at the town of Hailar which tied down some of the Soviet forces. At the same time, Soviet airborne units were used to seize airfields and city centers in advance of the land forces, and to ferry fuel to those units that had outrun their supply lines. The Soviet pincer from the east crossed the Ussuri and advanced around Khanka Lake and attacked towards Suifenhe, and although Japanese defenders fought hard and provided strong resistance, the Soviets proved overwhelming. Perhaps the most glaring fact illustrating the differences in efficacy between the two opponents was that, often, the speed of Soviet advances far outpaced any sort of fighting withdrawal the Japanese could conduct, which formed a crucial element of the entire Japanese strategy for defending the Manchurian heartland.

After a week of fighting, during which Soviet forces had penetrated deep into Manchukuo, Japan's Emperor Hirohito recorded the Gyokuon-hōsō which was broadcast on radio to the Japanese nation on August 15, 1945. The idea of surrender was incomprehensible to the Japanese people, and combined with Hirohito's use of formal and archaic language, the fact that he did not use the actual word "surrender", the poor quality of the broadcast, and poor lines of communication, there was some confusion amongst the Japanese about what the announcement actually meant. The Imperial Japanese Army Headquarters did not immediately communicate the cease-fire order to the Kwantung Army, and many elements of the army either did not understand it, or ignored it. Hence, pockets of fierce resistance from the Kwantung Army continued, and the Soviets continued their advance, largely avoiding the pockets of resistance, reaching Mukden, Changchun and Qiqihar by August 20. On the Soviet right flank, the Soviet-Mongolian Cavalry-Mechanized Group had entered Inner Mongolia and quickly took Dolon Nur and Kalgan. The Emperor of Manchukuo (and former Emperor of China), Puyi, was captured by the Soviet Red Army. The cease-fire order was eventually communicated to the Kwantung Army, but not before the Soviets had made most of their territorial gains.

On August 18, several Soviet amphibious landings had been conducted ahead of the land advance: three in northern Korea, one in Sakhalin, and one in the Kuril Islands. This meant that, in Korea at least, there were already Soviet soldiers waiting for the troops coming overland. In Sakhalin and the Kurils, it meant a sudden and undeniable establishment of Soviet sovereignty.

The land advance was stopped a good distance short of the Yalu River, the beginning of the Korean peninsula, when even the aerial supply lines became unavailable. The forces already in Korea were able to establish a bit of control in the peninsula's north, but the ambition to take the entire peninsula was cut short when American forces landed at Incheon on September 8, six days after the signing of the Japanese Instrument of Surrender.

Importance and consequences
From the time of the first major Japanese military defeats in the Pacific, the non-military leaders of Japan had come to realise that the Japanese military campaign was economically unsustainable, and there were a number of initiatives to negotiate a cessation of hostilities and the consolidation of Japanese territorial and economic gains. Hence, elements of the non-military leadership had first made the decision to surrender as early as 1943; the major issue was the terms and conditions of surrender, not the issue of surrender itself. For a variety of diverse reasons, none of the initiatives were successful, the two major reasons being the Soviet Union's deception and delaying tactics, and the attitudes of the "Big Six", the powerful Japanese military leaders. (Refer to Surrender of Japan for more detail.)

The Manchurian Strategic Offensive Operation, along with the atomic bombings of Hiroshima and Nagasaki, combined to break the Japanese political deadlock and force the Japanese leaders to accept the terms of surrender demanded by the allies.

In the "Sixty years after Hiroshima" issue of the Weekly Standard, American historian Richard B. Frank points out that there are a number of schools of thought with varying opinions of what caused the Japanese to surrender. He describes what he calls the "traditionalist" view, which asserts that the Japanese surrendered because the Americans dropped the atomic bombs. He goes on to summarise other points of view.

Tsuyoshi Hasegawa's research has led him to conclude that the atomic bombings were not the principal reason for Japan's capitulation. He argues that Japan's leaders were impacted more by the swift and devastating Soviet victories on the mainland in the week following Joseph Stalin's August 8 declaration of war because the Japanese strategy to protect the home islands was designed to fend off a US invasion from the South, and left virtually no spare troops to counter a Soviet threat from the North. This, according to Hasegawa, amounted to a "strategic bankruptcy" for the Japanese and forced their message of surrender on August 15, 1945. Others with similar views include The "Battlefield" series documentary, Drea, Hayashi, and numerous others, though all, including Hasegawa, state that the surrender was not due to any single factor or single event.

The Soviet invasion and occupation of the defunct "Manchukuo" marked the start of a traumatic period for the more-than-one-million occupants of the puppet state who were of Japanese descent. The situation for the Japanese military occupants was clear, but the Japanese colonists who had made "Manchukuo" their home, particularly those born in "Manchukuo", were now stateless and homeless, and the (non-Japanese) Manchurians wanted to be rid of these foreigners. Many were killed, many others ended up in Siberian prisons for up to 20 years, and some made their way to the Japanese home islands, where they were also treated as foreigners.

Manchuria was "cleansed" by Soviet forces of any potential military resistance. With Soviet support for the spread of Communism, Manchuria provided the main base of operations for Mao Zedong's forces, who proved victorious in the following four years of the Chinese Civil War. These military successes in Manchuria and China by the Communist Chinese led to the Soviet Union giving up their rights to bases in China — promised by the Western Allies — because all of the deemed-by-the-Soviets-to-be-"Chinese"-land which had been gained by the Soviets, (as distinct from what the Soviets considered to be "Soviet"-land-which-had-been-occupied-by-the-Japanese), was eventually turned over to the People's Republic of China. Note, however, that before leaving Manchuria, Soviet forces and bureaucracy dismantled almost all of the portable parts of the considerable Japanese built industry in Manchuria and relocated it to "restore industry in war-torn Soviet territory". That which was not portable was either disabled or destroyed; the Soviets had no desire for Manchuria to be an economic rival, particularly to the underdeveloped Far Eastern Soviet Territories.

As agreed at Yalta, the Soviet Union had intervened in the war with Japan within three months of the German surrender, and they were therefore entitled to the territories of Sakhalin and the Kuril Islands and also to preeminent interests over Port Arthur and Dalian, with its strategic rail connections. The territories on the Asian mainland were subsequently transferred to the full control of the People's Republic of China in 1955; the other possessions are still administered by the Soviet Union's successor state, Russia.

Though the north of the Korean peninsula was under Soviet control, the logistic machine driving the Soviet invasion forces had given out before the entire peninsula could be seized. With the American landing at Incheon — some time before the Red Army could have remobilized and secured the entire peninsula — Korea was effectively divided. This was a precursor to the Korean War five years later.

Japanese Monographs
The "Japanese Monographs" and the "Japanese Studies on Manchuria" - The 187 Japan Monographs are a series of operational histories written by former officers of the Japanese army and navy under the direction of General Headquarters of the U.S. Far East Command.
 * Monographs of particular relevance to Manchuria are:
 * No. 77 Japanese preparations for Operations in Manchuria (1931–1942)
 * No. 78 The Kwangtung Army in the Manchurian Campaign (1941–1945) Plans and Preparations
 * No. 119 Outline of Operations prior to the Termination of War and activities connected with the Cessation of Hostilities (July - August 1945)
 * No. 138 Japanese preparations for Operations in Manchuria (January, 1943 - August 1945)
 * No. 154 Record of Operations against Soviet Russia, Eastern Front (August 1945)
 * No. 155 Record of Operations against Soviet Russia, Northern and Western Fronts (August - September 1945)
 * List of the 13 Studies on Manchuria
 * Vol. I Japanese Operational Planning against the USSR (1932–1945)
 * Vol. II Imperial Japanese Army in Manchuria (1894–1945) Historical Summary
 * Vol. III STRATEGIC STUDY ON MANCHURIA MILITARY TOPOGRAPHY AND GEOGRAPHY Terrain Study
 * Vol. IV AIR OPERATIONS (1931–1945) Plans and Preparations
 * Vol. V INFANTRY OPERATIONS
 * Vol. VI ARMOR OPERATIONS
 * Vol. VII SUPPORTING ARMS AND SERVICES
 * Vol. VIII LOGISTICS IN MANCHURIA
 * Vol. IX CLIMATIC FACTORS
 * Vol. X Japanese Intelligence Planning against the USSR (1934–1941)
 * Vol. XI Small Wars and Border Problems
 * Vol. XII Anti-Bandit Operation (1931–1941)
 * Vol. XIII Study of Strategic and Tactical peculiarities of Far Eastern Russia and Soviet Eastern Forces (1931–1945)