Kantokuen
Kantokuen called for seven Japanese armies to invade and occupy the Russian Far East. Most of the empire's naval and air forces backed them, making it the largest combined arms operation in Japanese history to that point. The name is short for Kantōgun Tokushu Enshū, Kwantung Army Special Maneuvers, chosen to sound like nothing at all. The plan called for a three-step readiness phase, then three offensive phases meant to isolate and destroy Soviet defenders within six months. It never fired a shot. Within months, momentum drained away, and the operation was abandoned. What convinced the Imperial Japanese Army that Siberia was worth an operation this large, and what finally made its leaders let it go?
The Russo-Japanese War of 1904-1905 already had Tokyo working to limit tsarist influence in East Asia, years before the Soviet Union existed. When the Russian Civil War threatened to spread Bolshevism through the region, Japan sent roughly 70,000 troops into Siberia between 1918 and 1922. Fighting alongside the White movement, the Japanese occupied Vladivostok and other points east of Lake Baikal. Once that intervention ended and the Soviet government consolidated its hold, the Imperial Japanese Army kept drawing up plans for a future war. Those early plans were defensive, expecting a Red Army push into Chinese territory to be met by a Japanese counterattack out of Korea. The decisive battle, in this thinking, would fall in southern Manchuria. Everything shifted after Japan invaded Manchuria in 1931, leaving Japanese and Soviet troops facing each other across a border thousands of kilometers long. To defend the new puppet state of Manchukuo and seize the initiative before the Red Army could, the Army switched strategies. It would now stop any Soviet advance at the frontier, then carry the fight into Siberia itself. One account calls this shift an 'epoch-making change' in Japanese strategic thinking. That offensive posture held until 1945, by which point Japan faced catastrophe in the Pacific War. Over those same years, Japanese planning grew from small border operations into schemes for seizing the entire Soviet Far East, out to Lake Baikal.
By 1937, Japanese-Soviet relations had sunk to a low point, with both sides sensing a crisis building at the border. The Kwantung Army, Japan's occupation force in Manchuria, had grown from a minor garrison command into a full army group acting almost on its own. Tokyo often accepted its insubordination and unilateral aggression as a fait accompli rather than rein it in. As the Kwantung Army's power grew, border clashes with the Soviets worsened. They culminated in the Kanchazu Island incident, when Japanese shore batteries sank a Soviet river gunboat and killed 37 personnel. Combined with political and military subversion on both sides, these episodes convinced Soviet and Japanese figures alike that a showdown was likely, even inevitable. The outbreak of the Second Sino-Japanese War in July 1937 suddenly narrowed Japan's options in Manchuria and eased the threat to Siberia. The Soviets moved to capitalize, signing the Sino-Soviet Non-Aggression Pact that year and beginning to supply the Chinese with weapons and equipment. On the 13th of February 1938, Pravda reported that Japan's army numbered about 1,200,000 men, with 2,000 planes, 1,800 tanks, and 4,500 heavy artillery pieces. It noted that roughly 1,000,000 of those troops, and most of the arms, were already committed to the war in China. Despite that predicament, Japan kept building war plans against the Soviet Union. Its 1937 operational plan, though crude and logistically weak, became the basis for everything that followed until 1945. It called for a sudden opening blow against the Soviet Maritime Province, known as Primorye, paired with holding actions in the north and west. If that first phase succeeded, the other fronts would shift to the offensive once reinforcements arrived. In 1936, Soviet General Secretary Joseph Stalin launched the Great Purge, killing or imprisoning hundreds of thousands of his own people. Army officers were among them, often on invented charges. The Red Army's fighting power was badly weakened. Poor showings at the Battle of Lake Khasan in 1938, and again in the Winter War against Finland in 1940, seemed to confirm it. Fear pushed some Soviet officials to defect. On the 13th of June 1938, Genrikh Lyushkov, the NKVD's chief for the Far East, crossed into Manchuria and surrendered to the Imperial Japanese Army. He brought with him a wealth of secret documents on Soviet military strength and troop positions in the region. Lyushkov's defection became a major intelligence coup for Japan. He kept working against the Soviet Union until he vanished during the Soviet invasion of Manchuria in August 1945.
In 1938 and 1939, the Operations Bureau of the Japanese Army General Staff worked with the Kwantung Army on a pair of plans. Together these were known as Operational Plan No. 8, or 'Hachi-Go.' Concepts A and B both examined an all-out war against the Soviet Union starting in 1943. Both dwarfed anything the Japanese had conceived before. Against an expected 60 Soviet divisions, the Army would commit up to 50 of its own, fed in gradually from China and the Home Islands. Concept A closely mirrored the 1937 plan, attacking across Manchuria's eastern and northern borders while holding defensively in the west. The more ambitious Concept B aimed to strike into the open steppe between the Great Khingan Mountains and Lake Baikal. The goal was to cut the Trans-Siberian Railway quickly and isolate the whole region from European Russia. The scope was enormous: a front nearly 5,000 kilometers, or 3,100 miles, long. Japan's final objectives reached up to 1,200 kilometers into Soviet territory. In terms of sheer distance, Concept B would have dwarfed even Operation Barbarossa, Germany's June 1941 invasion of the Soviet Union. Manchuria's railway network, however, had not been expanded enough to support Concept B, and the supplies on hand fell well short of what it required. The ongoing war in China also made it impossible to gather the planned 50 divisions without crippling the fight there. Imperial General Headquarters calculated that reaching Lake Baikal would require some 200,000 motor vehicles. That was more than twice as many as the entire Japanese Army had ever possessed at one time. Support for Concept B collapsed after the 1939 Battle of Khalkhin Gol exposed how hard it was to supply even a small force far from railheads. From then on, Japanese planning centered on the northern and eastern fronts, with any western advance limited to the far slope of the Great Khingan range.
Toward the end of his life, Adolf Hitler reportedly voiced regret that Japan never joined his war against the Soviets. He is quoted as saying, 'We would together have exterminated Bolshevism before the winter of 1941.' From Tokyo's side, though, Germany's attitude toward joint action against the Soviets between 1939 and 1941 looked more like ambivalence, even duplicity. After Japan's defeat at Khalkhin Gol, the sudden announcement of the Molotov-Ribbentrop Pact landed as a shock and an insult. Japan read it as a direct violation of the Anti-Comintern Pact and a betrayal of shared interests. So in April 1941, Japan felt free to sign its own Neutrality Pact with the Soviets. Tension with the United States was already rising over Japan's occupation of Vichy French Indochina the year before. Allied economic sanctions piled up through 1940 and 1941. The growing threat of war in the south, paired with calm in the north, pulled Japanese attention away from the long-planned Siberian campaign. The Navy, which traditionally favored Nanshin-ron, or southward expansion, welcomed the shift, in contrast to the Army's preference for Hokushin-ron, or northward expansion. So it came as a genuine shock when Germany launched Operation Barbarossa against the Soviet Union in June 1941. Prime Minister Fumimaro Konoe, calling it a 'second betrayal,' even considered abandoning the Tripartite Pact. Foreign Minister Yosuke Matsuoka argued the opposite: Japan should drop its Neutrality Pact with the Soviets and attack alongside Germany. Both the Kwantung Army and powerful figures on the Army General Staff backed him. Among them was Major General Shin'ichi Tanaka, chief of the Operations Bureau, who wanted a 'quick decision.' This push for war collided with Japan's existing policy of flexible response, called Junbi Jin Taisei, or 'Preparatory Formation Setup.' Under that doctrine, intervention against the Soviets would happen only if the war in Europe turned clearly in Japan's favor. Though only formally articulated in June, Junbi Jin held firm against renewed pressure from the 'Go North' faction and shaped Japanese strategy through 1941. Its first real test came at an emergency Army-Navy conference on the 24th of June, called in the wake of Barbarossa. There, the 'Go North' faction clashed directly with its 'Go South' opponents. The compromise: the Army could prepare to invade Siberia if conditions allowed, but not at the expense of simultaneous planning for war in the south. Disagreement remained over how, and when, to resolve what officials called the 'northern question.' The dispute took its name from the metaphor of 'the persimmon.' Hardliners in the Army General Staff and Kwantung Army wanted to attack even while the fruit was 'still green,' before any Soviet collapse against Germany. Their opponents, focused on the Western powers and the war in China, wanted to wait until it had 'ripened and fell.' The Army General Staff concluded that any 1941 offensive had to finish by mid-October, since Siberia's brutal winter would halt military operations. If the Army needed 60-70 days to prepare and six to eight more weeks to win the first phase, its window for action was narrow. The General Staff drafted a 'crash schedule' to save time. Mobilization would be decided by the 28th of June, orders issued on the 5th of July, and troop concentration begun on the 20th of July. Hostilities were to be decided by the 10th of August and readiness completed by the 24th. Combat operations were to begin no later than the 10th of September, with the first phase of the war finished by the 15th of October. In total, the General Staff called for 22 divisions and 850,000 men, including auxiliary units, backed by 800,000 tons of shipping. Best case, the Japanese hoped the Soviets would halve their Far Eastern infantry while scrambling to fight Hitler. They also hoped Soviet armored and air strength would drop by two thirds, giving the Kwantung Army a two-to-one advantage. The War Ministry disagreed, preferring a more modest reinforcement of only 16 divisions between the Kwantung and Korea Armies. The Kwantung Army itself considered that force too weak for anything beyond mopping up after a German victory.
On the 5th of July 1941, Major General Shin'ichi Tanaka paid a personal visit to War Minister Hideki Tojo. Tanaka, chief of the Operations Bureau and co-leader of the 'Strike North' faction, won Tojo's backing that day. He wanted a far larger reinforcement of Manchuria than the War Ministry preferred, up to 25 divisions, disguised under the smaller 16-division stance the Ministry already favored. It moved in two stages. First came a buildup and readiness phase, called the No. 100 setup. Then came an offensive stance under the No. 101 and 102 setups, when the Kwantung Army would wait for the order to attack. With Tojo on board, General Hajime Sugiyama visited the Imperial Palace two days later to secure Hirohito's sanction. He promised the Kwantung Army would not attack on its own initiative. Operationally, Kantokuen mirrored the War Plan of 1940 but with a smaller force, 20 to 30 divisions instead of 43. It banked on the Soviets' inability to reinforce the Far East while fighting Germany. Even so, it stood as by far the largest mobilization in the history of the Japanese Army. Railways in the north and east had to be expanded, and port facilities, military housing, and hospitals enlarged to support it. As in the plans drawn up after the Nomonhan Incident, the opening blow would fall on the Ussuri Front against Primorye, followed by a second attack north toward Blagoveshchensk and Kuibyshevka. Under the First Area Army, the Japanese Third and Twentieth Armies would break through south of Lake Khanka and threaten Vladivostok. The 19th Division of the Korea Army reinforced them. At the same time, the Fifth Army would strike just south of Iman, now called Dalnerechensk. That would seal off the Maritime Province and sever the Trans-Siberian Railway, blocking reinforcements from the north. In the north, the Fourth Army would hold the Amur River line before turning to the offensive against Blagoveshchensk. Two more divisions, outside the main Kantokuen structure, were to attack Northern Sakhalin from land and sea in a pincer movement. Further objectives included Khabarovsk, Komsomolsk, Skovorodino, Sovetskaya Gavan, and Nikolayevsk, along with amphibious landings contemplated against Petropavlovsk-Kamchatsky and the Kamchatka Peninsula. The exact allocation of forces kept shifting through July. On the 9th, the Kwantung Army floated a direct strike on Khabarovsk instead of Blagoveshchensk. The Army General Staff rejected the idea for lack of a developed plan. On the 29th of July, the Kwantung Army settled on an all-out offensive along the Ussuri Front alone, holding elsewhere until the first stage succeeded. Meetings between Tojo and Tanaka on the 31st confirmed that sequence. The total was set at 24 divisions, at least 17 of them on the Eastern Front. The entire Kwantung Army reserve, five more divisions, was massed at Mutanchiang, near the eastern border. By the 16th of September, the plan called for 1,200,000 men, 35,000 motor vehicles, 500 tanks, 400,000 horses, and 300,000 laborers. That force was meant to sustain three months of offensive operations. That left the Western Front, facing the Mongolian People's Republic, defended by only the 23rd Division, veterans of Khalkhin Gol two years earlier. The Japanese hoped delaying actions across the Gobi Desert and Hailar Plain would serve as a buffer instead. Air power was meant to open the campaign. Some 1,200 to 1,800 planes in three air divisions would reinforce the 600 to 900 already in Manchuria. Together with roughly 350 Navy aircraft, they were to launch a sudden strike on Soviet air power in the Far East. Success there would let Japanese aircraft turn to supporting ground troops, cutting Soviet supply lines, and blocking reinforcements flown in from Europe.
A single railway line, the Trans-Siberian, carried nearly everything the Soviet Far East needed from European Russia, and Japanese planners saw that dependence as its greatest weakness. Roughly 6 million people lived in the region, most of them in cities rather than farmland, which left it short of both food production and reservists. Japanese intelligence calculated that the railway's limited capacity capped any Red Army force it could carry east at the equivalent of 55 to 60 divisions. To hold the border anyway, Soviet engineers had spent years building hundreds of hardened bunkers, called Tochkas, arranged into fortified belts along the frontier. The most common type, a hexagonal DOT, had an interior five to six meters across, with walls of solid concrete a meter or more thick. It usually held two or three machine guns, sometimes a 76 mm gun as well. These strongpoints sat 400 to 600 meters apart, in rows two to four deep, forcing any attacker into costly frontal assaults on prepared positions. By 1941, two Soviet commands faced the border: the Far Eastern Front under General Iosif Apanasenko, and the Trans-Baikal Front under General Mikhail Kovalyov. Together the two fronts fielded roughly 650,000 men, 5,400 tanks, and 3,000 aircraft, though those numbers fell sharply once Germany invaded. Between the 22nd of June 1941 and the 9th of May 1945, the Soviets pulled 344,676 men and 2,286 tanks from the Far East. Most of them left before early 1943, to fight the Wehrmacht. Mongolian forces, who had fought alongside the Soviets at Khalkhin Gol, added close to 80,000 more men to the region despite lacking heavy weapons. On the Japanese side, the Kwantung Army's best tank, the Type 97 Chi-Ha, carried thicker armor than the Soviet BT and T-26. Its gun, though, was weaker, only 57 mm against the 45 mm weapons the Soviets mounted. In the air, Japanese pilots held a real edge. Navy airmen averaged roughly 700 hours of flight time by late 1941, and Army pilots about 500. German pilots, by comparison, received only about 230 hours. Soviet pilots received even fewer. Many of these men had already fought in China. Several officers stationed with the Kwantung Army would later become well-known Pacific War names, among them Tomoyuki Yamashita, Isamu Yokoyama, Mitsuru Ushijima, and Tadamichi Kuribayashi. One account called the Kwantung Army 'the cream of the entire Japanese armed forces.' Yet the two sides understood logistics on entirely different scales. At Nomonhan, the IJA treated a distance of 100 kilometers as 'far' and 200 trucks as 'many.' Zhukov, by contrast, moved his army group with more than 4,000 vehicles on a 1,400-kilometer round trip from the nearest railheads. Zhukov himself credited that logistics feat to his superior, Grigory Shtern. Japan's own ammunition math made the gap plain: General Tanaka calculated each division needed three kaisenbun of supply, yet Japan's factories produced only 19 kaisenbun in all of 1941. Committing to a 24-division Kantokuen would have meant gambling roughly two thirds of the entire Japanese ammunition stockpile on the campaign's opening blow.
By mid-July 1941, Foreign Minister Yosuke Matsuoka's continued push for immediate war against the Soviets ended in his dismissal, replaced by Admiral Teijiro Tono. That was a serious blow to the 'Strike North' faction. General Hideki Tojo and Emperor Hirohito both still supported reinforcing Manchuria, but neither was ready to commit to actual war. Hirohito, in particular, worried about the Kwantung Army's volatility and the negative image its 'special maneuvers' created abroad. His concern was not misplaced. In October 1941, Brigadier General Sherman Miles of US Military Intelligence urged Washington to send direct military aid to the Soviet and Chinese armies, alarmed by the buildup in Manchuria. Time itself worked against the plan, too; later versions spoke of overrunning Primorye in 21 days, down from the original estimate of six to eight weeks. Meanwhile, the Soviet transfers west had been considerable, but manpower in the Far East stayed high, nowhere near the 50 percent cut Japanese planners had hoped for. General Shunroku Hata objected to weakening his China Expeditionary Army for Manchuria's sake, and incoming Korea Army commander Seishiro Itagaki agreed. Chief of Staff Hajime Sugiyama still won Hirohito's reaffirmed support on the 1st of August. Events had already overtaken them. On the 24th of July, Japan occupied key points in southern French Indochina. President Franklin Roosevelt answered by freezing all Japanese assets in the United States, citing an 'unlimited national emergency,' and Britain and the Dutch government-in-exile followed his lead. On the 1st of August, the same day Sugiyama stood before the Emperor, the United States imposed a total oil embargo on Japan. American exports had supplied 80 percent of Japan's oil, with most of the rest coming from the Dutch East Indies, which also refused to sell. On the 9th of August 1941, barely a week later, the Army General Staff yielded to the War Ministry, and plans to seize Southeast Asia took top priority instead. The Kantokuen buildup was capped at 16 divisions, meant only to stand guard, support diplomacy with Stalin's government, or seize a sudden opportunity if one appeared. In total, the reinforcement had brought 463,000 men, 210,000 horses, and 23,000 vehicles into Manchuria, along with 55,000 more men for the Korea Army. The 51st Division left for China that September, and by year's end IGHQ had also pulled another 88,000 men south, dropping Manchuria's garrison to 620,000 men. General Tanaka, still hoping for a 'golden opportunity' to strike north before the 1942 spring thaw, lost his temper when a logistics colonel warned that troops lacked proper winter billeting. Tanaka erupted, yelling that such 'nonsensical things' should not be said, and slapped the colonel. Common sense won out afterward, and the Kwantung Army pulled back from the border to wait out the winter. When Japan struck the Allies in December 1941, the depleted Kwantung Army played only a minor part. By the spring of 1942, with an increased war budget, IGHQ rebuilt Manchuria's garrison to its peak strength: 700,000 men, 900 tanks, and 900 aircraft, still without any real plan to fight the Soviets. That peak did not last. As the Pacific War worsened, division after division was pulled out of Manchuria to plug the empire's crumbling defenses, seven divisions in June and July 1944 alone, followed by an eighth, the 23rd, that October. Two of the Kwantung divisions sent to reinforce Formosa in the winter of 1944 to 1945 included the 9th, whose loss so alarmed Okinawa's commander, Lieutenant General Mitsuru Ushijima, that he warned, 'If the 9th Division is detached and transferred, I cannot fulfil my duty of defending this island.' By January 1945, the Kwantung Army had shrunk to only 460,000 men in nine divisions, with not a single division left to defend Korea and just 120 working aircraft in all of Manchuria. Some infantry companies had only one or two officers left, and entire artillery regiments had no guns at all. By August 1945, frantic last-minute mobilization had raised the count back to 714,000 men in 24 divisions and 12 brigades, but most of the new units, staffed by the old, the sick, colonists, and students, fought at barely 15 percent combat effectiveness. Of 230 combat planes still on hand, only 55 were considered modern. After the war, Colonel Saburo Hayashi admitted what the numbers already showed: 'We wanted to provide a show of force. If the Russians only knew the weakness of our preparations.'
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Common questions
What was Kantokuen?
Kantokuen was an operational plan created by the General Staff of the Imperial Japanese Army for the invasion and occupation of the Russian Far East, drawn up to capitalize on the outbreak of the Soviet-German War in June 1941. It would have involved seven Japanese armies and a major portion of Japan's naval and air forces, making it the largest combined arms operation in Japanese history up to that point.
When was Kantokuen approved?
Emperor Hirohito gave partial approval to the Kantokuen buildup on the 7th of July 1941, after General Hajime Sugiyama visited the Imperial Palace to request his sanction and promised that the Kwantung Army would not attack on its own initiative.
Why was Kantokuen abandoned?
Kantokuen fell out of favor at Imperial General Headquarters as preparations for a Southeast Asia offensive grew, the Second Sino-Japanese War kept draining resources, and prospects for a swift German victory over the Soviets dimmed. It was finally abandoned after the United States and its allies imposed an oil embargo and other economic sanctions in August 1941.
How many Japanese armies were involved in the Kantokuen plan?
The plan involved seven Japanese armies, backed by a major portion of the empire's naval and air forces.
Who was Genrikh Lyushkov and how did he affect Japanese planning against the Soviets?
Genrikh Lyushkov was the chief of the Far Eastern Department of the Soviet NKVD who defected to Japan on the 13th of June 1938, crossing into Manchuria with a wealth of secret documents on Soviet military strength and dispositions. His defection was a major intelligence coup for Japan, and he continued working against the Soviet Union until he disappeared during the Soviet invasion of Manchuria in August 1945.
What effect did the Kantokuen buildup have on the Soviet Union even though the invasion never happened?
The presence of large Japanese forces in Manchuria forced the Soviets, who had long anticipated an attack from that direction, to retain considerable military resources in Siberia throughout World War II.
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