'Kantokuen' was a Japanese plan created by the general staff of the Imperial Japanese army for an invasion and occupation of the far eastern region of the USSR (June/August 1941).

Known in full as the Kantogun Tokubetsu Enshu (Kwantung Army Special Manoeuvres), the 'Kantokuen' plan was designed to capitalise on the outbreak of the German-Soviet war in June 1941, and was partially approved by the Emperor Hirohito on 7 July. In overall terms, the plan involved a three-step readiness phase followed by a three-phase offensive intended to isolate and destroy the Soviet defenders within a maximum of six months. However, after growing conflict with simultaneous preparations for an offensive against South-East Asia, together with the demands of the 2^nd Sino-Japanese War and the steadily reducing likelihood of a swift German victory in Europe, 'Kantokuen' began to fall out of favour at the Imperial General Headquarters and was eventually abandoned altogether following increased sanctions by the USA late in July and early in August 1941.

The origins of anti-Russian (and then anti-Soviet) feeling in Japan dated back to the later part of the 19^th century. Eager to limit Russia’s influence in eastern Asia in the aftermath of the Russo-Japanese War of 1904/05 and then to contain the spread of Bolshevism from 1917, the Japanese sent some 70,000 troops into Siberia from 1918 to 1922 as part of the Entente powers' intervention on the side of the White (anti-Bolshevik) movement, occupying Vladivostok and many key points in Russia to the east of Lake Baikal. Following the international withdrawal from Russian/Soviet territory, the Imperial Japanese army fully appreciated the USSR’s longer-term potential as a military power and, keeping with the convention of Russia/USSR as a traditional enemy, developed a series of contingency plans in the event of a war with the Soviets. These plans were initially defensive, and assumed an aggressive attack by the Soviet army into Chinese territory which would then be countered by a Japanese counter-thrust from Korea. Japanese strategic thinking was therefore based on a decisive battlefield in southern Manchuria. After the Japanese invasion and annexation of that region in 1931, Japanese and Soviet troops for the first time faced one another along a border of very great length. Motivated by the desire to protect their Manchurian puppet state, now known as Manchukuo, and to seize the initiative in the event of war, the Imperial Japanese army adopted a policy of halting any Soviet advance along the border and ultimately fighting the greater part of the war on Siberian soil. This marked a major strategic change in Japanese military thinking by paving the way to a change from defensive to offensive planning. This thinking was reversed only in 1945. During this time the Japanese operational plans began to evolve from the small-scale operations originally envisaged into a series of multi-phase offensive actions directed initially against Vladivostok and then the whole of the Soviet Far East as far to the west as Lake Baikal.

In the period before the outbreak of the 2^nd Sino-Japanese war in July 1937, the nature of relations between Japan and the USE started to deteriorate sharply. The Kwantung Army responsible for control of Manchukuo had already been raised from the status of a minor garrison command to the level of a general headquarters, and now began to develop an increasingly bellicose attitude toward the USSR. This army began steadily to act as a self-contained and indeed autonomous entity independent of the central government in Tokyo: this was an attitude which, if left unchecked, could and in fact did spell disaster for Japan. With the Kwantung Army's unfettered attitude and conduct came a corresponding and inevitable increase in the number and extent of border skirmishes between Japanese and Soviet troops, culminating in the Kanchazu Island incident of 30 June 1937 in which a Soviet gunboat of the Amur River Flotilla was sunk by Japanese shore batteries, resulting in the deaths of 37 Soviet personnel. This and other border episodes, combined with each side’s efforts to subvert the other side politically and military, paved the way to the Japanese recruitment of White Russian agents and Soviet matériel support to China both before and during the war with Japan, and also led senior political and military figures on both sides to conclude that a future war was likely or, in the case of the Kwantung Army, inevitable.

After the start of the 2^nd Sino-Japanese War, the Japanese options for Manchukuo became very straitened, and the Soviets quickly attempted to capitalise on this Japanese weakness by signing a non-aggression pact with China, which the USSR supplied with weapons and equipment. This did not prevent Japan from continuing to create war plans against the USSR, however, and though crude very poorly conceived in logistical terms, the Japanese plan of 1937 provided the basis for all subsequent developments up to 1944. This and related plans were based on a pre-emptive attack on the Soviet Maritime Province (Primorsky Krai) facing the Pacific Ocean in combination with holding actions in the north and west. Should the first phase prove successful, the other fronts would then switch to the offensive after they had been reinforced.

During this period the USSR was undergoing extreme turbulence. From 1936 Iosif Stalin, the Soviet leader, launched a series of devastating purges on the Soviet army’s officer corps. Many thousands of middle- and high-ranking officers were executed or imprisoned, generally on trumped up or fictitious charges. These purges severely degraded the Soviet army’s operational capability, as indicated by its relatively poor showing in the Battle of Lake Khasan (otherwise the Changkufeng Incident) of 29 July/11 August 1938 and the 'Talvisota' winter war between 30 November 1939 and 13 March 1940. The terror resulting from the Stalinist purges also persuaded many of those in fear of their lives to defect or flee abroad. On 13 June 1938, for example, Commissar 3^rd Rank Genrikh S. Lyushkov, chief of the Far Eastern Department of the NKVD internal security apparatus, crossed the border into Manchukuo and surrendered himself to the Imperial Japanese army: Lyushkov brought with him a wealth of secret documents on Soviet military strengths and dispositions in the region. This was a major intelligence coup for Japan, and Lyushkov continued to work against the USSR up to the time of his disappearance during the Soviet 'Manchurian Strategic Offensive Operation' invasion of August 1945.

Independent of their yearly planning, in 1938/39 the operations department of the Imperial Japanese army’s general staff and the Kwantung Army co-operated on the development of two related contingency plans under the umbrella term 'Operational Plan No. 8', otherwise the 'Hachi' plan. These two schemes, designated Concept A and Concept B, considered the possibility of an all-out war with the USSR from 1943. Both plans were considerably larger than anything previously considered by the Japanese inasmuch as they called for the commitment of 50 divisions against an estimated 60 Soviet divisions, these Japanese formations coming from China and the home islands. Concept A was based on Japanese traditional concepts, with offensives in the east and north and only defensive undertakings in the west, while Concept B entertained the possibility of an initial offensive into the vast steppe between the Great Khingan mountains and Lake Baikal in the hope of scoring an early decisive blow, leaving the Soviet forces in the Primorye and Vladivostok areas of the Pacific coast for subsequent defeat in detail. The scope of the envisaged operations was hue: the two sides would have fought over a front of almost 3,110 miles (5000 km), and Japan’s ultimate objectives were no less than 745 miles (1200 km) into the USSR.

Despite the ambition of their concepts, the Japanese were nonetheless compelled to acknowledge several harsh realities preventing any shorter-term implementation of 'Hachi'. With regard to Concept B, the expansion of the railway network in Manchukuo was inadequate to ensure the matériel support of so huge an undertaking, and the stocks of supplies within the country were drastically short of the required levels. Furthermore, the continuing 2^nd Sino-Japanese War made it impossible to concentrate the planned 50 divisions without a fatal weakening of the Japanese effort in China. The Imperial General Headquarters also reached the conclusion that the sustenance of an offensive to Lake Baikal would require some 200,000 trucks, which was a figure more than twice as great as anything the entire Japanese military possessed at any given time. Popular support for Concept B within Imperial Japanese army faded in 1939 after the Japanese defeat in the Battle of Khalkin Gol had demonstrated the monumental difficulty of supplying a sustained military commitment on even a relatively limited scale so far away from the nearest rail heads. From that time onward, Japanese planning for offensive operations against the USSR became focused primarily on the northern and eastern fronts, with any advances in the west limited to relatively small-scale advances on the western slops of the Great Khingan range.

Toward the end of his life, the German leader Adolf Hitler is reported to have said that '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.' From the Japanese perspective, however, Germany’s attitude with regard to German and Japanese co-operation against the USSR between 1939 and 1941 was at best ambivalent and at worst duplicitous. After Japan’s defeat at Khalkin Gol, Germany’s sudden signature of a non-aggression pact with the USSR elicited both shock and anger in Japan, which saw in this a direct violation of the Anti-Comintern Pact of November 1936 and a betrayal of the two nations' common interests. In April 1941, therefore, Japan felt free to conclude its own Neutrality Pact with the Soviets as tension with the western nations, most especially the USA, began to mount over the Japanese 'Fu' (i) occupation of the northern part of Vichy French Indo-China in the previous year. As US economic sanctions began to exercise an increasingly burdensome effect on Japan, the growing threat of war in the south and the sense of supposed 'tranquility' in the north started to shift Japanese attention away from the long-planned campaign in Siberia. This change was welcomed most particularly by the Imperial Japanese navy, which traditionally favoured a policy of southward aggression while maintaining a deterrent against the USSR.

Thus it was with considerable shock and consternation that the Japanese government received the news of the 'Barbarossa' invasion of the USSR in June 1941. The Japanese prime minister, Prince Fumimaro Konoye, mortified about what he perceived as this 'second betrayal' of Japan, for a short time considered Japan’s withdrawal from the Tripartite Pact. The foreign minister, Yosuke Matsuoka, on the other hand immediately called for the abandonment of the Neutrality Pact with the USSR, of which he himself had been the architect, and demanded an attack in support of Germany. Matsuoka’s views were supported by both the Kwantung Army and the general staff of the Imperial Japanese army, who were eager for a 'quick decision'. Before the start of 'Barbarossa', at a time earlier in June the Japanese government had decided on a policy of 'flexible response' in order to establish situation of military readiness in case of a need to take the offensive to the north or the south. This Junbi Jin Taisei (Preparatory Formation Setup) contemplated intervention in the event of a Soviet-German war, though only in the event that events took eventuated in a manner favourable for Japan. Although it was not always so clear-cut, this philosophy ultimately defined Japanese strategic thinking throughout 1941.

The Junbi Jin Tasei encountered its first serious test when an emergency meeting of the highest-ranking army and navy leaders was convened on June 24 to establish a new national policy reflecting the situation in the USSR. During this meeting the Imperial Japanese army argued vigorously for the use of force against Siberia, while the Imperial Japanese navy opposed it. Eventually there emerged a compromise in which the army would be allowed to intervene against the USSR should the circumstances permit, thought it was also decided that preparations for this eventuality must not interfere with the concurrent planning for the 'Strike South' ('Centrifugal Offensive') in the south. Although this arrangement was accepted in principle, there was still disagreement over exactly how the army would resolve the 'northern question' and the timing of such a resolution. The basic conflict can be summarised in the metaphor of 'the persimmon', with the general staff of the army and the Kwantung Army arguing for an offensive even if the fruit was 'still green' (even if the USSR had not suffered a catastrophic collapse against Germany), and their opponents opting for a more conservative approach, assigning less immediacy to the Manchukuoan front in the light of Japan’s wider strategic position. From the general staff’s point of view, if Japan was to engage in hostilities during 1941 it was imperative that the fighting be over by the middle of October, bearing in mind the bitter climate characteristic of Siberia and northern Manchukuo. As a period of between 60 and 70 days would be required for the completion of operational preparations, and another 42 to 56 days to crush the Soviets in the territory between Manchukuo and the Pacific coast, the window of action available to the Japanese was distinctly limited. In response, the army’s general staff proposed for planning purposes a 'crash schedule' intended to trim as much time as possible: this schedule comprised a decision about mobilisation on 28 June; the issue of mobilisation orders on 5 July; the start of troop concentrations on 20 July; the yes/no decision about hostilities on 10 August; the completion of the readiness phase on 24 August; the concentration of two divisions from northern China in Manchukuo, raising the in-theatre strength to 16 divisions, on 29 August; the concentration of another four divisions from the home islands, bringing the total in-theatre strength to 22 divisions, on 5 September; the start of combat operations by 10 September at the latest; and the completion of the war’s first phase by 15 October.

Thus the army’s general staff called for 22 divisions with 850,000 men, including those of auxiliary units, supported by 800,000 tons of shipping to be made ready should war come with the Soviets. As whole, though, the war ministry was not in agreement with the army 'hawks'. Although the war ministry supported the notion of reinforcing the north, it preferred a far more modest limit of only 16 divisions allocated to General Yoshijiro Umezu’s Kwantung Army and General Kotaro Nakamura’s (from 7 July 1941 General Seishiro Itagaki’s) Korea Army in light of priorities elsewhere: this strength, the Kwantung Army started, would make its impossible to engage the Soviets with. The message sent was clear: Japan would wait until 'the persimmon' had ripened and fallen before taking the field against the Soviet army.

Angered by their initial setback by the war ministry, the hardliners of the Imperial Japanese army eventually secured a measure of revenge, at least in principle. During a personal visit on 5 July 1941, Major General Shinichi Tanaka, the operations chief of the army general staff and co-leader with Matsuoka of the 'Strike North' faction in Tokyo, managed to persuade the war minister, General Hideki Tojo, to support the army general staff’s opinions concerning the 'rightness' and 'viability' of reinforcing Manchukuo. Tanaka and his supporters pushed for a greater commitment than provided in the army’s plan of June 1941, to a total of 25 divisions, under the guise of establishing the readiness stance provided by the 16 divisions preferred by the war ministry. Tanaka’s plan was a two-stage scheme with a build-up and readiness phase (No. 100 set-up) followed by a offensive stance (Nos. 101 and 102 set-ups), after which the Kwantung Army would await the order to attack. I was this whole process which became known as 'Kantokuen'. With Tojo’s support for 'Kantokuen' secured, the hardliners then completed their circumvention of the war ministry on 7 July when General Hajime Sugiyama, the chief of the army general staff, visited the Imperial Palace to request Hirohito’s official authorisation for the build-up. After assurances from Sugiyama that the Kwantung Army would not take the offensive on its own initiative after receiving reinforcements, Hirohito assented.

In purely operational terms, 'Kantokuen' was essentially identical to the war plan of 1940 though scaled down from 43 to 25 divisions: this it thought to have arisen from the Japanese perception that the Soviets would not be able to reinforce their position in the Far East while so heavily committed against Germany in the west. The level of the Japanese commitment was, however, still enormous and in fact represented by far the largest single mobilisation in the history of the Imperial Japanese army. To facilitate the operation, huge quantities of combat and logistical assets would have to be dispatched to Manchukuo to boost the existing structure. In particular, to capitalise on the advantage offered to them by their interior lines of communication, the Japanese would have to expand the railway network in the north and east to handle the increased burden imposed by an offensive campaign. Moreover, port facilities, military accommodation and medical facilities would also have to be enlarged.

Like the previous concepts drawn up in the aftermath of the Nomonhan Incident, 'Kantokuen' would begin with a massive initial blow on the Ussuri river front to the east against Primorye by Lieutenant General Shigeichi Hada’s 5^th Army, Lieutenant General Kameji Seki’s 20^th Army, General Masakazu Kawabe’s 3^rd Army and Lieutenant General Yoshio Kozuki’s 19^th Division, followed by another attack to the north against Blagoveshchensk by Lieutenant General Kohei Washizu’s 4^th Army. Under command of the 1^st Area Army, the 3^rd Army and 20^th Army, supported by the 19^th Division of the Korea Army, were to penetrate the border in the area to the south of Lake Khanka and overwhelm the main Soviet defensive lines and threatening Vladivostok. Simultaneously, the 5^th Army was to attack in the area just to the south of Iman (now Dalnerechensk), completing the isolation of the Maritime Province, severing the Trans-Siberian Railway, and blocking any reinforcements arriving from the north. In northern Manchukuo, the 4^th Army was initially to hold the Amur river line before going over to the offensive with the task of taking Blagoveshchensk. Meanwhile, two reinforced divisions outside the 'Kantokuen' force structure were to start operations against the Soviet northern part of Sakhalin island from both the landward and seaward sides with the aim of wiping out the defenders there in a pincer movement. Finally, Lieutenant General Touji Yasui’s 6^th Army in the north-west of Manchukuo was to remain on the defensive to prevent any Soviet assault on Qiqihar from the area of Zabaikalsk.

To ensure the success of this single most critical phase of the the planned campaign, 'Kantokuen' was based on the commitment of overwhelming strength in the form of 1.2 million men, 35,000 trucks, 500 tanks, 400,000 horses and 300,000 labourers in 23 to 24 divisions for the offensive on the eastern front alone after a preparatory three-month build-up. This would have meant, however, that the north-western front facing Mongolia and the Trans-Baikal region could be defended by only one or two divisions plus the equivalent of a few more divisions in border guard units. Indeed, during the initial phase of operations the 6^th Army was allocated only Lieutenant General Kanji Nishihara’s 23^rd Division and the 8^th Border Guard Unit, both of them veterans of the fighting at Khalkin Gol two years earlier. To minimise the possibility of a Soviet counter-offensive in the north-west while the bulk of the Kwantung Army was committed in the east, the Japanese hoped that delaying actions, in combination with the vast expanses of the Gobi Desert and Hailar plain would serve as strategic buffers preventing any realistic Soviet threat to the heart of Manchukuo before the main Japanese strength could be regrouped for a pivot to the north-west. The final objective of the Japanese troops was a line running through Skovorodino and the western slopes of the Great Khingan mountains, along which they would defeat the remaining Soviet forces and transition to a defensive stance.

As in any modern military operation, air power played a crucial role in the 'Kantokuen' plan. Before the outbreak of the Pacific War in December 1941, the Japanese intended to dispatch some 1,200 to 1,800 warplanes of three air divisions to bolster the existing 600 to 900 aircraft already in Manchukuo. This air strength was to co-operate with about warplanes of the Imperial Japanese navy in the launch of a sudden and annihilating attack on the Soviet Far Eastern air forces both in the air and on the ground at the outset of hostilities. In the event that they succeeded, the Japanese air units were then to have focused their efforts on the support of the ground forces at the tactical level, cutting the Soviet lines of communication and supply, especially in the Amur and Trans-Baikal regions, and preventing the the arrival of Soviet air reinforcements from Europe.

In sum, the Japanese forces involved in operations against the USSR from Mongolia to Sakhalin island would have totalled some 1.5 million men, 2,000 tanks, large quantities of artillery, between 2,100 and 3,100 aircraft, 40,000 trucks and 450,000 horses.

In preparing their plans for any future war in the Far East, Japanese and Soviet strategic planning was dominated by two fundamental geopolitical realities: firstly, the Soviet Far East and Mongolian People’s Republic constituted a horseshoe around Manchukuo over a border more than 2,800 miles (4500 km) long; and secondly, the Soviet Far East was dependent both economically and militarily on European Russia via the single Trans-Siberian Railroad.

It was this second factor which constituted the basic foundation of the vulnerability of the USSR’s Far Eastern areas in any war with Japan. At only some 6 million, the Far East’s population was small, and a relatively high percentage of this population was concentrated in urban rather than rural environments, suggesting an emphasis on industry. Thus the comparatively small scale of the local agricultural output meant that there would be a deficiency in food production for both civilian and military purposes, as well as a smaller pool of potential reservists. Despite being allocated considerable resources in the Second and Third Five-Year Plans of 1933/42, there were still major difficulties. Although the Soviets relied on the Trans-Siberian Railway to send people, food and raw materials eastward to overcome the major deficits (sometimes even forcibly resettling discharged soldiers in Siberia), this created another problem inasmuch as the limited capacity of the Trans-Siberian Railway also restricted the maximum size of any Soviet military forces which could be deployed against Japan, which the Japanese estimated would amount to the equivalent of 55 to 60 divisions.

Any protracted disruption of the Trans-Siberian Railway would therefore prove fatal to both the Far Eastern regions and any Soviet attempt to defend them. Such disruption was a feat which could be accomplished with ease by the Japanese side as the tracks ran parallel with the frontier for very long distances, and sometimes even coming to within artillery range of the Manchukuoan frontier. Moreover, while the encircling geography of the USSR and Mongolia was a theoretical advantage for offensive operations by giving the Soviet forces the opportunity to undertake a strategic envelopment of Manchukuo, for defensive operations the extended nature of their military groupings led these latter vulnerable to isolation and piecemeal destruction at the hands of a more compact opponent. Although the Soviets made concerted efforts to address this vulnerability, such as beginning work on a 2,485-mile (4000-km) extension of the Trans-Siberian Railway as the BAM Line, these alone were insufficient to overcome the basic weakness of the Soviet position.

The limitations of the Trans-Siberian Railway and the remote nature of the Far Eastern regions was both an advantage and a disadvantage to each side. Although the combination prevented the Soviets from concentrating and supplying vast numbers of men against a Japanese invasion and granted the latter an effective means of isolating the territory from European Russia, it also ensured that Japan alone could never inflict a decisive strategic defeat on the USSR because the latter’s primary military and economic assets would remain unharmed in the more western parts of the country. The general staff of the Imperial Japanese army therefore arrived at the conclusion that only an offensive on two fronts, in Europe and Asia, against the USSR’s vital industrial centres and aimed at destroying its political will to resist could ever succeed in bringing about the destruction of the USSR.

In a time late in the 1930s into 1941, Soviet strategic planning against Japan was basically defensive and intended primarily to preserve the continued existence of its Far Eastern regions and the Mongolian People’s Republic. The means to this end were not to be wholly passive, however. Even after Germany’s 'Barbarossa' invasion of the USSR and well into 1942, the Stavka recommanded an all-out defence of the border zone and weighty counterattacks all along the front with the aim firstly of preventing the Imperial Japanese army from capturing Soviet territory and secondly of driving its back into Manchukuo. While the aggressive language used by Komandarm 1^st Rank Boris M. Shaposhnikov, the chief of the Soviet general staff, during 1938 advocating 'decisive action' in northern Manchukuo after a 45-day period had by 1941 been toned down to 'destroying the first echelon' of invaders and 'creating a situation of stability', the Soviet army never entirely forsook the concept of limited offensive goals. The Japanese assessed that the limited extent of traversable terrain between the Manchurian border and the Pacific Ocean, and the vulnerability of the Trans-Siberian Railway in the Amur and Primorye regions, were the two factors which compelled the Soviets to adopt this posture, despite the considerable Soviet investment of resources to fortify the area for defensive warfare.

The primary major formations responsible for protecting the USSR from Japanese aggression in 1941 were General Iosif R. Apanasenko’s Far Eastern Military District (later Front) and General Leytenant Mikhail P. Kovalev’s Trans-Baikal Military District (later Front). Based on nine divisions (including two tank), one mechanised brigade and one fortified region, the Trans-Baikal Front was tasked with defending the area to the west of the Oldoy river near Skovorodino, while with 23 divisions (including three tank), four brigades (excluding anti-aircraft) and 11 fortified regions, the Far Eastern Front guarded the land to the east, including the crucial seaport of Vladivostok. Combined, the two fronts had some 650,000 men, 5,400 tanks, 15,000 pieces of artillery, 3,000 aircraft, 57,000 motor vehicles and 95,000 horses.

In addition to this, by 1942 the Vladivostok Defence Sector also possessed some 150 pieces of artillery in calibres between 76 and 356 mm (3 and 14.4 in) organised into 50 batteries. Of these weapons, the most numerous was the 130-mm (5.1-in) B-13, whose 90 examples constituted the equipment of 20 batteries.

However, after the 'Barbarossa' invasion of the western USSR, Soviet forces in the Far East underwent a radical transformation. Even before the start of 'Barbarossa', the Soviet army had started a steady transfer of men and matériel westward to Europe: before 22 June 1941, therefore, the above figures had already been reduced by 57,000 men, 1,070 tanks and 670 pieces of artillery from five divisions. Then, between 22 June and 1 December, another 2,209 machines were sent to the European front, and during the same period 13 other divisions with 122,000 men, 2,000 pieces of artillery and mortars, 1,500 tractors, and nearly 12,000 motor vehicles were also detached from the Far East, along with a Japanese estimate of 1,800 aircraft. Between 22 June 1941 and 9 May 1945 and mostly by a time early in 1943, a total of 344,676 men, 2,286 tanks, 4,757 pieces of artillery and mortars, 11,903 motor vehicles, and 77,929 horses were removed from the Far Eastern and Trans-Baikal Fronts to bolster the Soviet forces in the west.

In spite of a marked reduction in matériel strength, the Soviets made a huge effort to increase their conscription of men in an expansion paralleling the massive Japanese build-up in Manchukuo, which was easily assessed by Soviet and Chinese observers as a result of its size. In accordance with the Soviet general mobilisation ordered 22 July 1941, the combined strength of the Trans-Baikal Front and Far Eastern Front was to be increased to more than 1 million men by 2 August, and by 20 December the actual figure was 1.161 million men, of whom 1.129 million regular officers or enlisted men, and the balance cadets or course attendees. Despite the Far East regions' limited population, this expansion of active personnel was achieved through the addition of reservists from the Ural, Central Asian, and Siberian Military Districts. Furthermore, the standing strengths of the NKVD and Soviet navy were also boosted: between 22 June and 15 November 1941, naval manpower in the Far East rose from 94,199 to 169,029, while that of the NKVD border troops, which mustered slightly fewer than 34,000 before the war, is believed to have been increased to slightly more than 60,000. Lastly there were the contribution of the Mongolians, who despite their lack of heavy weaponry had earlier proved themselves against the Japanese at Khalkin Gol and would later go on to participate in the invasion of Manchuria in August 1945: though the Mongolians lacked the experience and organisation of the Soviets, their numbers approached 80,000.

Had 'Kantokuen' been launched late in August or early in September 1941 the USSR and Mongolia could have fielded about 1.1 million men, 3,200 tanks, 14,000 pieces of artillery, 2,000 aircraft, 51,000 motor vehicles and 117,000 horses. Of these, about two-thirds of all personnel (including virtually the entire naval element) would have been deployed on the Amur river-Ussuri river-Sakhalin island front while the remainder would have been undertaking the defence of Mongolia and the Trans-Baikal region; matériel was divided more evenly between the two groupings.

Even though the situation of their forces fighting the Germans and their allies in Europe was acute, Soviet planners continued to adhere to essentially the pre-war concept for operations in the Far Eastern regions and Manchuria. Under this strategy, during the opening days of hostilities the Far Eastern Front, headquartered in Khabarovsk, together with Vitse Admiral Ivan S. Yumashev’s Pacific Fleet, was ordered to conduct an all-out defence of the border, not allowing the Japanese onto Soviet territory and holding Blagoveshchensk, Iman (Dalnerechensk), and the entirety of Primorye regardless of cost. The main defensive effort was to be mounted by the 1^st Army and 25^th Army (the former based at Vladivostok) on a north-south axis between the Pacific Ocean and Lake Khanka, while the 35^th Army would dig in at Iman. To the north, the 15^th Army and 2^nd Red Banner Army, based at Birobidzhan and Blagoveshchensk respectively, were to repel all Japanese assaults from the far bank of the Amur river. Meanwhile, the Soviets would stand firm on Sakhalin, Kamchatka, and the Pacific Coast, and try to deny the Sea of Okhotsk to the Imperial Japanese navy. To support this effort, the Soviet army had for some years undertaken a determined programme of fortification construction along the borders with Manchuria: this involved the construction of several hundreds of hardened fighting positions backed by trenches in the fortified regions. These were well-sited: as there were only a limited number of roads crossing the frontier area, which was both hilly and forested, the Soviets could be confident that each avenue of approach was covered by prepared defences which would have to be overcome by means of costly frontal attacks, so delaying the Japanese and compelling them to pay heavily in men and equipment. To counter the Soviet prepared defences, the Japanese had to keep considerable quantities of heavy artillery near the border, these pieces ranging from more modern 240- and 300-mm (9.45- and 11.8-in) howitzers to antiquated 280-mm (11-in) weapons dating from the time of the Russo-Japanese War (1904/05). As an added precaution, in the aftermath of the Battle of Khalkin Gol, the Imperial Japanese army distributed for the use of its 300-mm (11.8-in) weapons a special one-ton shell with a range of only 915 yards (1000 m): these shells were designed to shatter a strongpoint with a single hit.

Despite the advantages they derived from the frontier terrain and belt of fixed defences, the Soviet army had no intention of maintaining the defensive and outlasting a Japanese assault. The Stavka ordered that by the fifth day of war the troops of the 15^th Army and 35^th Army (less the 66^th Division), together with the Amur Red Banner Military Flotilla and any available reserves, to defeat the Japanese forces opposite them, force the Amur and Ussuri river, and launch a counter-offensive co-ordinated against both sides of the Sungari river in Manchukuoan territory. The final objectives of the Soviet forces along the Sungari river were the cities of Fujin and Baoqing, which were to be reached on the 25^th day of hostilities. The object of this attack was to stabilise the front and also to relieve pressure on the Ussuri railway and Khabarovsk areas. Similarly, the other Soviet forces would also begin short counterblows right across the front in accord with the Soviet doctrine that defensive action cannot be successful without the co-ordination of positional defence and counterattack.

Simultaneously, on the opposite side of Manchukuo, the 17^th Army and 36^th Army of the Trans-Baikal Front, headquartered at Mt Shirlova in the Yablonovy range, were to hold for three days and then counterattack, advancing to Lakes Buir and Hulun by the tenth day of the war.

Given the USSR’s critical position in the 'Great Patriotic War' in the west, reinforcements for the Far Eastern forces from the hinterland were relatively small: just four tank brigades, five artillery regiments, six guards mortar regiments, and five armoured train divisions were provided for the support of both fronts.

With the aim of supporting the Soviet army’s ground battle, the air forces and navy were also to have an active role. In the case of the air forces, the primary task was the destruction of Japanese aircraft both in the air and on the ground, followed by tactical ground-attack missions against Japanese troops to assist the progress of the Sungari river offensive. Other objectives for the air forces included the destruction of railways, bridges and airfields in Manchukuo and Korea, as well as the interception of troop transports and warships in the Sea of Japan in co-ordination with the warships and warplanes of the Pacific Fleet. Strategic bombing was to be limited to a mere 30 Ilyushin DB-3 warplanes, which were to be despatched in groups of eight to 10 aircraft against targets in Tokyo, Yokosuka, Maizuru and Ominato. Concurrently, the Soviet naval forces would attempt to effect the immediate closure of the mouth of the Amur river, the mining of the Tatar Strait, and the defence of the Pacific coast from any possible Japanese landing, thereby liberating the 25^th Army in Primorye from coast defence duty. Submarine patrols would begin in the Yellow Sea, Sea of Okhotsk and Sea of Japan with the aim of preventing the transport of troops from the Japanese home islands to the Asian mainland, and of disrupting Japanese maritime communications. Soviet submarines were ordered not to approach the Japanese coast, but rather to operate defensively close to home territory.

It should be noted that the Soviet plans, like those of the Japanese opposition, were open-ended in nature with no clearly defined resolution. Hence, both implicitly relied on outside factors to force a conclusion that they themselves could not force.

Both of the prospective belligerents faced difficulties which could have impeded the attainment of their goals. In the case of the Japanese, although their war in China, now four years old, had provided them with a wealth of combat experience, their understanding and application of concepts such as modern military logistics and massed firepower still lagged behind those of the Soviet army. At the time of the Nomonhan Incident the Imperial Japanese army regarded distances of 60 miles (100 km) as 'far' and 200 trucks as 'many', while Komkor Georgi K. Zhukov had more than 4,000 vehicles for the supply of his Soviet-Mongolian Forces; Group of Forces on an 870-mile (1400 km) round trip from the nearest railheads. To compensate for their lack of numbers and their limited resources, the Japanese relied on intangible factors such as fighting spirit to overcome the foe, but this alone was insufficient. Although the Imperial Japanese army’s appreciation of 20^th century military realities improved in the months and years after the fact, and the Kwantung Army's matériel strength was radically upgraded during the build-up of 1941, their fundamental reliance on fighting spirit to create victory in battle never changed, sometimes even at the expense of logical thinking and common sense: traditionalism and unwillingness to change sometimes actively impeded improvements to both technology and doctrine, to the point where those who argued for change were accused of 'faint-heartedness' and 'insulting the Imperial army'. Toward the end of the war in the Pacific the pendulum began to swing in the opposite direction, with Japanese leaders grasping at 'wonder weapons' such as jet fighters and a so-called 'death ray' in the hope of reversing their fortunes.

The Soviets, on the other hand, operated under the shadow of the 'Great Patriotic War' in the west. While the Far Eastern Front and Trans-Baikal Front had access to a formidable array of weaponry, the demands of the fighting in Europe meant that strength was drawn from them on an almost weekly basis. Moreover, the state of the vehicles which remained was often mixed: before the start of westward transfers in 1941 some 660 tanks and 347 aircraft were unserviceable as a result of repair needs or other causes. Because the Soviets possessed only a limited offensive capability on the Primorye and Trans-Baikal axes, they could never hope to achieve a decisive victory over the Kwantung Army even if they succeeded in slowing or stopping the Japanese. Furthermore, attacking into the teeth of a prepared opponent, especially one with his own fortified regions and heavy concentrations of troops immediately opposite the border, was the hardest kind of offensive requiring overwhelming numbers and massive means of assault for success: the Soviets possessed neither of these.

The Soviet forces in the Far East were deployed, or perhaps dispersed, along a great arc from Mongolia in the west to Vladivostok in the east. Lacking the capability to capitalise on this deployment by striking deep into Manchukuo along several convergent axes, their strength would be fatally diluted and prone to piecemeal destruction at the hands of the Japanese, who could manoeuvre without hindrance using their interior lines of communication, concentrating their power at will while the immobile Soviets were fixed in place. The only saving grace for the Soviets was the fact that the very remoteness of the Far East from European Russia made impossible for the Japanese alone from defeating the USSR, for which it would be reliant on Germany.

Organisationally, although Soviet forces in the Far East on paper amounted to the equivalent of some 32 divisions by December 1941, they were regarded as only barely sufficient for defensive operations. Compared to a typical Japanese division, pre-war Soviet divisions had only slightly more than half the manpower strength, but had greater access to long-range higher-calibre artillery. After the German invasion, however, the Soviet Army was reorganized so that each division had less than half the manpower and a fraction of the firepower of either its German or Japanese counterpart. Hence, to achieve superiority on the battlefield the Soviets would have to concentrate several divisions to counter each of its opponent’s divisions.

Lastly, the quality of both personnel and equipment cannot be ignored. As the Soviets drained their best-trained divisions to fight in the west, the overall standard of the forces in the east correspondingly diminished, forcing the Stavka to rely more heavily on its fortified regions in defensive operations. Meanwhile, the Kwantung Army opposite them then constituted the cream of the entire Japanese armed forces, and was receiving daily reinforcement. A large proportion of its units were elite Type A divisions, each with between 26,654 and 25,874 men, many of which had seen extensive service in China. The quality of the Japanese officer corps was also very high, as many figures who would go on to have notable careers in the Pacific War including Tomoyuki Yamashita, head of the Kwantung Defence Command and later the 1^st Area Army; Isamu Yokoyama, commander of the 1^st Division and later the 4^th Army; Mitsuru Ushijima, commander of the 11^th Division; and Tadamichi Kuribayashi, commander of the 1^st Cavalry Brigade and later the Mongolia Garrison Army.