[4] 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 favor at Imperial General Headquarters and was eventually abandoned after increased economic sanctions by the United States and its allies.

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.

[18] 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.

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.

In response, the Army General Staff proposed a "crash schedule" for planning purposes intended to "shave off" as much time as possible:[37] All in all, the AGS called for 22 divisions with 850,000 men (including auxiliary units) supported by 800,000 tons of shipping to be made ready for the war with the USSR.

With Tojo's support for Kantokuen secured, the hardliners completed their circumvention of the War Ministry on July 7, when General Hajime Sugiyama visited the Imperial Palace to request Hirohito's official sanction for the build up.

According to Japanese intelligence, FER's lack of self-sufficiency was exacerbated by the fact that a high proportion of its small population (about 6 million people in total)[66] was concentrated in urban, rather than rural, environments,[67] which created a deficiency in food production for both soldiers and civilians as well as a smaller pool of potential reservists.

Although the Soviets traditionally relied on the Trans-Siberian Railway to send manpower, food, and raw materials eastward to overcome the major deficiencies (sometimes even by forcibly resettling discharged soldiers in Siberia),[69] this created another problem since the limited capacity of that railroad also restricted the maximum size of any Red Army force that could be brought to bear on Japan, which the Japanese estimated to be the equivalent of 55 to 60 divisions.

[70] Thus, any prolonged disruption of the Trans-Siberian Railway would ultimately prove fatal to FER and to any Soviet attempt to defend it, something that was well within Japanese capabilities as the tracks ran parallel to the frontier for thousands of kilometers and sometimes even came to within artillery range of the Manchurian border.

Furthermore, though the encircling geography of the Soviet Union and Mongolia theoretically gave the Red Army an opportunity for a strategic envelopment of Manchuria,[73] on the defensive the strung out Russian groupings would be vulnerable to isolation and piecemeal destruction.

Although they prevented the Red Army from concentrating its full might against the Japanese and provided the latter with an effective means of isolating the region from European Russia, they also ensured that Japan alone could never administer a decisive defeat to the Soviet Union because the latter's main military and economic assets would remain unharmed.

Even after the German invasion and well into 1942, Stavka advocated for an all-out defense of the border zone and heavy counterattacks all along the front, with the objective of preventing the IJA from seizing any Soviet territory and throwing it back into Manchuria.

Although the aggressive language used by Boris Shaposhnikov in 1938 concerning "decisive action" in northern Manchuria after 45 days[77] had by 1941 been moderated to simply "destroying the first echelon" of invaders and "creating a situation of stability,"[78] the Red Army never totally gave up limited offensive goals.

The Japanese assessed that the lack of traversable terrain between the Manchurian border and the Pacific Ocean combined with the vulnerability of the Trans-Siberian Railway in the Amur and Primorye regions compelled them to take such a stance, despite investing considerable resources to fortify the area for defensive warfare.

[89] On the whole, between June 22, 1941, and May 9, 1945, a total of 344,676 men, 2,286 tanks, 4,757 guns and mortars, 11,903 motor vehicles, and 77,929 horses were removed from the Far Eastern and Trans-Baikal Fronts to bolster the desperate fighting against the Wehrmacht,[90] the vast majority of whom arrived before early 1943.

[106] Under this strategy, during the opening days of hostilities the Far Eastern Front (with its headquarters at Khabarovsk) together with the Pacific Fleet was ordered to conduct an all-out defense of the border; prevent the Japanese from entering Soviet territory; and hold Blagoveshchensk, Iman (Dalnerechensk) and the entirety of Primorye "at all costs."

To help aid that effort, the Red Army had for years undertaken a determined fortification program along the borders with Manchuria that involved the construction of hundreds of hardened fighting positions backed by trenches, referred to as "Tochkas" (points).

According to a study prepared just before the outbreak of the Pacific War, it was estimated that Japan's capacity to produce Army ground ordnance would reach a peak of 50 kaisenbun during the 1942 fiscal year, or enough to sustain 50 divisions for four months.

In stark contrast to this, although the Trans-Siberian Railway imposed a limit on the size of the force the Soviets could bring to battle at any one time, their military industry as a whole, supported by Western aid, was able to sustain a grinding four-year war against Germany to a victorious close.

In addition, although their then four-year war in China had provided the Japanese with a large amount of combat experience, much of it translated only obliquely to a campaign against the Soviets, who had a firmer understanding of concepts such as massed firepower and motor-based logistics.

"[130] Toward the end of the Pacific War, the pendulum began to swing in the opposite direction, with Japanese leaders grasping at wonder weapons such as the Nakajima Kikka jet fighter and a so-called "death ray" in the hope of reversing their fortunes.

[134] Furthermore, as pointed out by Soviet General Sergey Shtemenko after the war, attacking into the teeth of a prepared enemy was "the hardest kind of offensive," which required "overwhelming numbers and massive means of assault" to succeed,[135] neither of which the Red Army had at the time.

[142] In general, the "handcrafted, beautifully polished" Japanese tanks were more survivable thanks to their diesel engines (the gasoline powerplants used by the Russians were especially fireprone[143]), but their smaller numbers meant that each loss was more damaging to the IJA than each destroyed "crudely finished" "expendable" BT or T-26 was to the Red Army.

By mid-July 1941, Foreign Minister Matsuoka's continued insistence for an immediate war against the Soviet Union ended in his dismissal and his replacement with Admiral Teijiro Tono, which dealt a blow to the "Strike North" faction.

After the initial phase of the Southern Offensive was brought to a close in the spring of 1942, IGHQ, conscious of the Kwantung Army's weakened state and hoping to make the most of an increased war budget, decided to reorganize and strengthen its troops in Manchuria.

Although the Kwantung Army held few illusions about its miserable state of affairs (its own "exhaustive studies" concluded that it had been weakened "far beyond estimation" and that new divisions formed to counterbalance the withdrawals possessed only a "fraction" of the fighting power of the originals), senior leaders continued to rationalize.

[199][w] The Soviets were very deliberate in their preparations: to prevent the Japanese from shifting forces to block an attack on a single front, it was determined that only an all-axes surprise offensive would be sufficient to surround the Kwantung Army before it had a chance to withdraw into the depths of China or Korea.

[201] Aware that the Japanese knew the limited capacity of the Trans-Siberian Railway would mean that preparations for an invasion would not be ready until autumn and that weather conditions would also be rather unfavorable before then, Soviet planners enlisted the help of the Allies to deliver additional supplies to facilitate an earlier offensive.

"[203] Even after the atomic bombing of Hiroshima on 6 August, there was no sense of crisis, and special war games (expected to last for five days and attended by a number of high-ranking officers) were conducted near the borders, with Yamada flying to Dairen to dedicate a shrine.

[209][y] In the end, as Foreign Minister Shigemitsu signed the unconditional surrender of Japan aboard USS Missouri in Tokyo Bay, the men of the vaunted Kantogun, having once dreamed of riding into Siberia as conquerors, instead found themselves trudging there as prisoners of war.