Kantokuen (, from , , "Kwantung Army Special Maneuvers"Coox p. 1041) was an operational plan created by the General Staff of the Imperial Japanese Army for an invasion and occupation of the Russian Far East, capitalizing on the outbreak of the Soviet–German War in June 1941. Involving seven Japanese armies and a major portion of the empire's naval and air forces, it would have been the largest combined arms operation in Japanese history up to that point, and one of the largest of all time.JSOM vol. I p. 147
The plan was approved in part by Emperor Hirohito on July 7 and involved a three-step readiness phase followed by a three-phase offensive to isolate and destroy the Soviet defenders within six months.Cherevko p. 27 After growing conflict with simultaneous preparations for an offensive in Southeast Asia, together with the demands of the Second Sino-Japanese War and dimming prospects for a swift German victory in Europe, Kantokuen fell out of favour at Imperial General Headquarters and was eventually abandoned after increased economic sanctions by the United States and its allies.Coox pp. 1046–1049
Nevertheless, 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.Glantz p. 60
Background The roots of anti-Soviet sentiment in Imperial Japan existed before the foundation of the Soviet Union itself. Eager to limit tsarist influence in East Asia after the Russo-Japanese War (1904–1905) and then to contain the spread of Bolshevism during the Russian Civil War, the Japanese deployed some 70,000 troops into Siberia from 1918 to 1922 as part of their intervention on the side of the White movement, occupying Vladivostok and other key points east of Lake Baikal.Humphreys p. 25JSOM vol. I p. 23 After the international withdrawal from Russian territory and the establishment of the Soviet regime, the Imperial Japanese Army, mindful of the Soviets' potential as a military power and in keeping with the convention of Russia as a traditional enemy, made contingency plans for a future war. Initially defensive in nature, they envisioned an invasion by the Red Army into Chinese territory that would then be parried by a Japanese counterattack from Korea, with the decisive battlefield being southern Manchuria.JSOM vol. I pp. 23–27 After the Japanese invaded Manchuria in 1931, Japanese and Soviet troops found themselves facing one another along a border thousands of kilometers in length. To protect the puppet state of Manchukuo and to seize the initiative early against the Red Army, the IJA adopted a policy of halting any Soviet advance along the border and fighting the greater part of the war in Siberia, an "epoch-making change" in Japanese strategic thought. The transition from the strategic defensive to the strategic offensive would not be reversed until 1945, when Japan was facing disaster during the Pacific War. Moreover, Japanese plans progressively increased in scope from relatively small-scale operations to gigantic multistage campaigns, which envisioned seizing virtually the entire Soviet Far East as far as Lake Baikal.JSOM vol. I pp. 29–31
1937 and beyond
Japanese-Soviet relations reached a low point by 1937, with an increasing sense of crisis on both sides.Coox p. 102 The Kwantung Army, Japan's occupation force in Manchuria, was openly hostile to the Soviets and appeared to be spoiling for a fight. This army, which expanded over time from a minor garrison command into a full-fledged army group, acted as a "self-contained, autonomous" entity almost entirely independent from the central government. The Kwantung Army's history was punctuated by a long record of insubordination and unilateral military aggression, which Tokyo often weakly accepted as a fait accompli. As the Kwantung Army's power increased, the Soviet–Japanese border conflicts worsened, culminating in the Kanchazu Island incident in which a Soviet river gunboat was sunk by Japanese shore batteries, killing 37 personnel.Coox p. 109 These episodes, together with reciprocal political and military subversion by both sides led both Soviet and Japanese figures to conclude that a future showdown was likely, even inevitable.Cherevko p. 19Coox pp. 118–119
After the outbreak of the Second Sino-Japanese War in July 1937, however, Japanese options in Manchuria suddenly became very limited, greatly reducing their potential threat to Siberia. The Soviets were eager to capitalize on this by signing the Sino-Soviet Non-Aggression Pact that year, and began supplying the Chinese with weapons and equipment. On February 13, 1938, Pravda triumphantly declared:
Despite their predicament, the Japanese continued to formulate war plans against the Soviet Union, and their operational plan of 1937, though crude and logistically deficient, provided the basis for all subsequent developments until 1945.JSOM vol. I pp. 20–21; 75–76. This plan called for a sudden initial onslaught against the Soviet Maritime Province facing the Pacific Ocean (also referred to as "Primorye"), coupled with holding actions in the north and west. If the first phase was successful, the other fronts would also transition to the offensive after receiving reinforcements.JSOM vol. I p. 61
While the Japanese were bogged down in China, the Red Army was experiencing its own disaster. In 1936, Soviet General Secretary Joseph Stalin began the Great Purge, killing or imprisoning hundreds of thousands of his own people, including army officers, often on trumped-up or fictitious charges. As a result, the Red Army's fighting power was severely weakened, an observation seemingly confirmed by poor showings at the Battle of Lake Khasan in 1938 and in the Winter War against Finland in 1940.Drea p. 14 Fear led some to defect or flee abroad, and on June 13, 1938, Genrikh Lyushkov, Chief of the Far Eastern Department of the NKVD, crossed the border into Manchuria and turned himself in to the IJA, bringing with him a wealth of secret documents on Soviet military strength and dispositions in the region. Lyushkov's defection was a major intelligence coup for Japan, and he continued to work against the USSR up until he disappeared during the Soviet invasion of Manchuria in August 1945.Coox pp. 123–128
Hachi-Go plans Independently of their yearly planning, the Operations Bureau of the Japanese Army General Staff and the Kwantung Army co-operated in 1938 and 1939 on a pair of related contingencies under the umbrella term "Operational Plan No. 8," or the "Hachi-Go""Hachi-Go" literally means "Eight-Five". plan. Both variants, designated Concepts "A" and "B," examined the possibility of an all-out war with the Soviet Union beginning in 1943.JSOM vol. I p. 105 Both were far larger than anything previously conceived of by the Japanese: against an expected 60 Soviet divisions, the IJA would commit up to 50 of its own, to be delivered incrementally from China and the Home Islands. Concept A closely mimicked the 1937 war plan by calling for attacks across the eastern and northern borders of Manchuria while maintaining a defensive stance in the west, but the more ambitious Concept B examined the possibility of striking out into the vast steppe between the Great Khingan Mountains and Lake Baikal in the hopes of quickly cutting the Trans-Siberian Railway. Such a move, the Japanese believed, would immediately isolate the whole region from European Russia and doom the remaining defenders to defeat in detail.JSOM vol. I pp. 106–108 The scope of operations was enormous: the two sides would be engaged over a front nearly 5,000 kilometers (3,100 miles) in length, with Japan's final objectives being up to deep into Soviet territory. In terms of distances, Concept B would have dwarfed even Operation Barbarossa, the German invasion of the Soviet Union in June 1941.
+Projected concentration of forces, Hachi-Go concept A Japan (50 divisions) USSR (60 divisions) Time D-Day D+60 D+90 D-Day D+60 D+90 Eastern Front 12 20 20 15 20 20 Northern Front 8 13 15 6 12 15 Western Front 3 8 15 9 18 25 Divs not yet arrived 27 9 0 30 10 0
+Projected concentration of forces, Hachi-Go concept B Japan (45 divisions) USSR (60 divisions) Time D-Day D+60 D+90 D-Day D+60 D+90 Eastern Front 5 8 10 15 18 18 Northern Front 3 8 10 6 12 12 Western Front 15 20 25 9 20 30 Divs not yet arrived 22 9 0 30 10 0
As impressive as these plans appeared in theory, however, the Japanese were forced to acknowledge several harsh realities preventing their implementation in the near future. Specifically with regard to Concept B, the railway network in Manchuria had not been sufficiently expanded to support such a far-reaching offensive, and the supplies on hand in the country were seriously below the required levels. Furthermore, the ongoing war in China precluded the concentration of the planned 50 divisions without fatally weakening the Japanese effort there. In addition, Imperial General Headquarters concluded that to sustain a drive out to Lake Baikal, a fleet of some 200,000 motor vehicles would be necessary,JSOM vol. I p. 108 more than twice as many as anything the entire Japanese Army ever had at a given time.USSBS p. 220 Popular support for Concept B finally dissipated in army circles after the 1939 Battle of Khalkhin Gol demonstrated the extensive challenges of sustaining even a small force so far away from the nearest railheads. From then on, Japanese offensive planning against the Soviets chiefly focused on the northern and the eastern fronts, with any western advances being limited to relatively modest gains on the far slope of the Great Khingan range.Coox p. 91
Decision 1941 Junbi Jin and "the persimmon"
Toward the end of his life, Adolf Hitler reportedly lamented: "It is certainly regrettable that the Japanese did not enter the war against Soviet Russia alongside us. Had that happened, Stalin's armies would not now be besieging Breslau and the Soviets would not be standing in Budapest. We would together have exterminated Bolshevism before the winter of 1941."Mawdsley, 'Conclusion' From the Japanese perspective, however, Germany's attitude toward cooperation against the Soviets from 1939 to 1941 was one of ambivalence, even duplicity.Coox pp. 1035–1036 After the Japanese defeat at Khalkhin Gol, the sudden unveiling of the Molotov–Ribbentrop Pact was met with shock and anger in Japan, where it was seen as a direct violation of the Anti-Comintern Pact and a betrayal of their common interests. Consequently, in April 1941 Japan felt free to arrange its own Neutrality Pact with the Soviets, as tension with the West, particularly the United States, began to mount over the Japanese occupation of Vichy French Indochina the previous year. Amid a barrage of Allied economic sanctions throughout 1940 and 1941, the growing threat of war in the south and the sense of "tranquility" in the north tended to divert Japanese attention away from the long-planned campaign in Siberia.Coox p. 1034JSOM vol. I p. 137 This shift was particularly welcomed by the Imperial Japanese Navy, which traditionally favored a policy of Nanshin-ron (southward expansion) while maintaining a deterrent against the Soviet Union, as opposed to the Hokushin-ron (northward expansion) favored by the Imperial Japanese Army.Coox p. 1037