3.175 Fall and Rise of China: Soviet-Japanese Border Conflicts

Last time we spoke about the Changsha fire. Chiang Kai-shek faced a brutal choice: defend Wuhan to the last man or flood the land to slow the invaders. He chose both, pushing rivers and rallying a fractured army as Japanese forces pressed along the Yangtze. Fortresses at Madang held long, but the cost was high—troops lost, civilians displaced, a city's heart burning in the night. Wuhan fell after months of brutal fighting, yet the battle did not break China's will. Mao Zedong urged strategy over martyrdom, preferring to drain the enemy and buy time for a broader struggle. The Japanese, though victorious tactically, found their strength ebbing, resource strains, supply gaps, and a war that felt endless. In the wake of Wuhan, Changsha stood next in the Japanese crosshairs, its evacuation and a devastating fire leaving ash and memory in its wake. Behind these prices, political currents swirled. Wang Jingwei defected again, seeking power beyond Chiang's grasp, while Chongqing rose as a western bastion of resistance. The war hardened into a protracted stalemate, turning Japan from an aggressive assailant into a wary occupier, and leaving China to endure, persist, and fight on.

#175 The Soviet-Japanese Border Conflicts

Welcome to the Fall and Rise of China Podcast, I am your dutiful host Craig Watson. But, before we start I want to also remind you this podcast is only made possible through the efforts of Kings and Generals over at Youtube. Perhaps you want to learn more about the history of Asia? Kings and Generals have an assortment of episodes on history of asia and much more so go give them a look over on Youtube. So please subscribe to Kings and Generals over at Youtube and to continue helping us produce this content please check out www.patreon.com/kingsandgenerals. If you are still hungry for some more history related content, over on my channel, the Pacific War Channel where I cover the history of China and Japan from the 19th century until the end of the Pacific War.

So based on the title of this one, you probably can see we are taking a bit of a detour. For quite some time we have focused on the Japanese campaigns into China proper 1937-1938. Now the way the second sino-japanese war is traditionally broken down is in phases. 1937-1938, 1939-1942 and 1942-1945. However there is actually even more going on in China aside from the war with Japan. In Xinjiang province a large full blown Islamic revolution breaks out in 1937. We will be covering that story at a later date, but another significant event is escalating border skirmishes in Manchukuo. Now these border skirmishes had been raging ever since the USSR consolidated its hold over the far east. We talked about some of those skirmishes prior to the Sino-Soviet war in 1929. However when Japan created the puppet government of Manchukuo, this was a significant escalation in tensions with the reds. Today we are going to talk about the escalating border conflicts between the Soviets and Japan.

A tongue of poorly demarcated land extends southeast from Hunchun, hugging the east bank of the Tumen River between Lake Khasan to the east and Korea to the west. Within this tongue stands Changkufeng Hill, one of a long chain of highlands sweeping from upstream along the rivers and moors toward the sea. The twin-peaked hill sits at the confluence area several miles northwest of the point where Manchuria, Korea, and the Russian Far East meet. The hill's shape reminded Koreans of their changgo, which is a long snare drum constricted at the center and tapped with the hands at each end. When the Manchus came to the Tumen, they rendered the phonetic sounds into three ideographic characters meaning "taut drum peaks" or Chang-ku-feng. The Japanese admired the imagery and preserved the Chinese readings, which they pronounce Cho-ko-ho. From their eastern vantage, the Russians called it Zaozernaya, "hill behind the lake." Soviet troops referred to it as a sugar-loaf hill.

For many years, natives and a handful of officials in the region cultivated a relaxed attitude toward borders and sovereignty. Even after the Japanese seized Manchuria in 1931, the issue did not immediately come to a head. With the expansion of Manchukuo and the Soviet Far East under Stalin's Five-Year plans, both sides began to attend more closely to frontier delimitation. Whenever either party acted aggressively, force majeure was invoked to justify the unexpected and disruptive events recognized in international law. Most often, these incidents erupted along the eastern Manchurian borders with the USSR or along the 350-mile frontier south of Lake Khanka, each skirmish carrying the seeds of all-out warfare.

Now we need to talk a little bit about border history. The borders in question essentially dated to pacts concluded by the Qing dynasty and the Tsardom. Between the first Sino-Russian Treaty of Nerchinsk in 1689 and the Mukden Agreement of 1924, there were over a dozen accords governing the borders. Relevant to Changkufeng were the basic 15-article Convention of Peking, supplementing the Tientsin Treaties of November 1860, some maps made in 1861, and the eight-article Hunchun Border Protocol of 1886. By the 1860 treaty, the Qing ceded to Tsarist Russia the entire maritime province of Siberia, but the meaning of "lands south of Lake Khanka" remained rather vague. Consequently, a further border agreement was negotiated in June 1861 known as "the Lake Khanka Border Pact", by which demarcations were drawn on maps and eight wooden markers erected. The border was to run from Khanka along ridgelines between the Hunchun River and the sea, past Suifenho and Tungning, terminating about 6 miles from the mouth of the Tumen.

Then a Russo-Chinese commission established in 1886 drew up the Hunchun Border Pact, proposing new or modified markers along the 1860–1861 lines and arranging a Russian resurvey. However, for the Japanese, in 1938, the Chinese or Manchu texts of the 1886 Hunchun agreement were considered controlling. The Soviets argued the border ran along every summit west of Khasan, thereby granting them jurisdiction over at least the eastern slopes of all elevations, including Changkufeng and Shachaofeng. Since the Qing dynasty and the house of Romanov were already defunct, the new sovereignties publicly appealed to opposing texts, and the Soviet side would not concede that the Russian-language version had never been deemed binding by the Qing commissioners. Yet, even in 1938, the Japanese knew that only the Chinese text had survived or could be located.

Now both the Chinese and Russian military maps generally drew the frontier along the watershed east of Khasan; this aligned with the 1861 readings based on the Khanka agreement. The Chinese Republican Army conducted new surveys sometime between 1915 and 1920. The latest Chinese military map of the Changkufeng area drew the border considerably closer to the old "red line" of 1886, running west of Khasan but near the shore rather than traversing the highland crests. None of the military delimitations of the border was sanctified by an official agreement. Hence, the Hunchun Protocol, whether well known or not, invaluable or worthless, remained the only government-to-government pact dealing with the frontiers.

Before we jump into it, how about a little summary of what became known as the Soviet-Japanese border conflicts. The first major conflict would obviously be the Russo-Japanese war of 1904-1905. Following years of conflict between the Russian Empire and Japan culminating in the costly Battle of Tsushima, Tsar Nicholas II's government sought peace, recognizing Japan's claims to Korea and agreeing to evacuate Manchuria. From 1918 to 1920, the Imperial Japanese Army, under Emperor Taishō after the death of Meiji, assisted the White Army and Alexander Kerensky against the Bolshevik Red Army. They also aided the Czechoslovak Legion in Siberia to facilitate its return to Europe after an Austrian-Hungarian armoured train purportedly went astray. By 1920, with Austria-Hungary dissolved and Czechoslovakia established two years earlier, the Czechoslovak Legion reached Europe. Japan withdrew from the Russian Revolution and the Civil War in 1922. Following Japan's 1919-1920 occupations and the Soviet intervention in Mongolia in 1921, the Republic of China also withdrew from Outer Mongolia in 1921. In 1922, after capturing Vladivostok in 1918 to halt Bolshevik advances, Japanese forces retreated to Japan as Bolshevik power grew and the postwar fatigue among combatants increased.

After Hirohito's invasion of Manchuria in 1931–1932, following Taishō's death in 1926, border disputes between Manchukuo, the Mongolian People's Republic, and the Soviet Union increased. Many clashes stemmed from poorly defined borders, though some involved espionage. Between 1932 and 1934, the Imperial Japanese Army reported 152 border disputes, largely tied to Soviet intelligence activity in Manchuria, while the Soviets accused Japan of 15 border violations, six air intrusions, and 20 cases of "spy smuggling" in 1933 alone. Numerous additional violations followed in the ensuing years. By the mid-1930s, Soviet-Japanese diplomacy and trust had deteriorated further, with the Japanese being openly labeled "fascist enemies" at the Seventh Comintern Congress in July 1935.

Beginning in 1935, conflicts significantly escalated. On 8 January 1935, the first armed clash, known as the Halhamiao incident, took place on the border between Mongolia and Manchukuo. Several dozen cavalrymen of the Mongolian People's Army crossed into Manchuria near disputed fishing grounds and engaged an 11‑man Manchukuo Imperial Army patrol near the Buddhist temple at Halhamiao, led by a Japanese military advisor. The Manchukuo Army sustained 6 wounded and 2 dead, including the Japanese officer; the Mongols suffered no casualties and withdrew after the Japanese sent a punitive expedition to reclaim the area. Two motorized cavalry companies, a machine‑gun company, and a tankette platoon occupied the position for three weeks without resistance.

In June 1935, the first direct exchange of fire between the Japanese and Soviets occurred when an 11‑man Japanese patrol west of Lake Khanka was attacked by six Soviet horsemen, reportedly inside Manchukuo territory. In the firefight, one Soviet soldier was killed and two horses were captured. The Japanese requested a joint investigation, but the Soviets rejected the proposal. In October 1935, nine Japanese and 32 Manchukuoan border guards were establishing a post about 20 kilometers north of Suifenho when they were attacked by 50 Soviet soldiers. The Soviets opened fire with rifles and five heavy machine guns. Two Japanese and four Manchukuoan soldiers were killed, and another five were wounded. The Manchukuoan foreign affairs representative lodged a verbal protest with the Soviet consul at Suifenho. The Kwantung Army of Japan also sent an intelligence officer to investigate the clash. On 19 December 1935, a Manchukuoan unit reconnoitering southwest of Buir Lake clashed with a Mongolian party, reportedly capturing 10 soldiers. Five days later, 60 truck‑borne Mongolian troops assaulted the Manchukuoans and were repulsed, at the cost of three Manchukuoan dead. On the same day, at Brunders, Mongolian forces attempted three times to drive out Manchukuoan outposts, and again at night, but all attempts failed. Further small attempts occurred in January, with Mongolians using airplanes for reconnaissance. The arrival of a small Japanese force in three trucks helped foil these attempts; casualties occurred on both sides, though Mongolian casualties are unknown aside from 10 prisoners taken.

In February 1936, Lieutenant-Colonel Sugimoto Yasuo was ordered to form a detachment from the 14th Cavalry Regiment to "drive the Outer Mongol intruders from the Olankhuduk region," a directive attributed to Lieutenant-General Kasai Heijuro. Sugimoto's detachment included cavalry guns, heavy machine guns, and tankettes. They faced a force of about 140 Mongolians equipped with heavy machine guns and light artillery. On February 12, Sugimoto's men drove the Mongolians south, at the cost of eight Japanese killed, four wounded, and one tankette destroyed. The Japanese began to withdraw, but were attacked by 5–6 Mongolian armored cars and two bombers, which briefly disrupted the column. The situation was stabilized when the Japanese unit received artillery support, allowing them to destroy or repel the armored cars.

In March 1936, the Tauran incident occurred. In this clash, both the Japanese Army and the Mongolian Army deployed a small number of armored fighting vehicles and aircraft. The incident began when 100 Mongolian and six Soviet troops attacked and occupied the disputed village of Tauran, Mongolia, driving off the small Manchurian garrison. They were supported by light bombers and armored cars, though the bombing sorties failed to inflict damage on the Japanese, and three bombers were shot down by Japanese heavy machine guns. Local Japanese forces counter-attacked, conducting dozens of bombing sorties and finally assaulting Tauran with 400 men and 10 tankettes. The result was a Mongolian rout, with 56 Mongolian soldiers killed, including three Soviet advisors, and an unknown number wounded. Japanese losses were 27 killed and 9 wounded. Later in March 1936, another border clash occurred between Japanese and Soviet forces. Reports of border violations prompted the Japanese Korean Army to send ten men by truck to investigate, but the patrol was ambushed by 20 Soviet NKVD soldiers deployed about 300 meters inside territory claimed by Japan. After suffering several casualties, the Japanese patrol withdrew and was reinforced with 100 men, who then drove off the Soviets. Fighting resumed later that day when the NKVD brought reinforcements. By nightfall, the fighting had ceased and both sides had pulled back. The Soviets agreed to return the bodies of two Japanese soldiers who had died in the fighting, a development viewed by the Japanese government as encouraging. In early April 1936, three Japanese soldiers were killed near Suifenho in another minor affray. This incident was notable because the Soviets again returned the bodies of the fallen servicemen.

In June 1937, the Kanchazu Island incident occurred on the Amur River along the Soviet–Manchukuo border. Three Soviet gunboats crossed the river's center line, disembarked troops, and occupied Kanchazu Island. Japanese forces from the IJA 1st Division, equipped with two horse-drawn 37 mm artillery pieces, quickly established improvised firing positions and loaded their guns with both high-explosive and armor-piercing shells. They shelled the Soviet vessels, sinking the lead gunboat, crippling the second, and driving off the third. Japanese troops subsequently fired on the swimming crewmen from the sunken ships using machine guns. Thirty-seven Soviet soldiers were killed, while Japanese casualties were zero. The Japanese Ministry of Foreign Affairs protested and demanded the Soviet forces withdraw from the island. The Soviet leadership, apparently shocked by the incident and reluctant to escalate, agreed to evacuate their troops.

By 1938 the border situation had deteriorated. The tangled terrain features, mountain, bog, stream, forest, and valley, would have complicated even careful observers' discernment of the old red line drawn in 1886. Fifty years later, the markers themselves had undergone a metamorphosis. Japanese investigators could find, at most, only 14 to 17 markers standing fairly intact between the Tumen estuary and Khanka—roughly one every 25 miles at best. The remainder were missing or ruined; five were found in new locations. Marker "K," for example, was 40 meters deeper inside Manchuria, away from Khanka. Japanese military experts noted that of the 20 markers originally set along the boundaries of Hunchun Prefecture alone, only four could be found by the summer of 1938. The rest had either been wrecked or arbitrarily moved and discarded by Russian or Chinese officials and inhabitants. It is even said that one missing marker could be seen on display in Khabarovsk. The Chinese had generally interpreted the boundary as the road line just west of Khasan, at least in practice. Free road movement, however, had become a problem even 20 years before the Japanese overran Manchuria in 1931–1932 during the so-called Manchurian Incident. The Japanese adopted, or inherited, the Chinese interpretation, which was based on the 1886 agreement on border roads; the key clause held that the frontier west of Khasan would be the road along the lake.

Japanese sources emphasize that local residents' anger toward gradual Soviet oppression and penetrations westward into Manchurian territory fueled the conflict. Many natives believed the original boundaries lay east of the lake, but the Soviets adjusted the situation to suit their own convenience. In practice, the Russians were restricting road use just west of Khasan by Manchurian and Korean residents. There was speculation that this was a prelude to taking over the ridgelines, depending on the reaction of the Manchukuoan–Japanese side. Villagers who went to streams or the lake to launder clothing found themselves subjected to sniper fire. Along a 25-mile stretch of road near Shachaofeng, farmers reported coming under fire from new Soviet positions as early as November 1935. Nevertheless, Japanese and Koreans familiar with the Tumen area noted agrarian, seasonal Korean religious rites atop Changkufeng Hill, including fattened pigs sacrificed and changgo drums beaten. Village elders told Japanese visitors in 1938 that, until early the preceding year, no Russians had come as far as Changkufeng Hill. Looking only at the border sector around Changkufeng, the easy days were clearly behind us. In the summer of 1938, Gaimusho "Foreign Ministry" observers described the explosive situation along the Korea–Manchuria–USSR borders as a matter of de facto frontiers. Both sides pressed against each other, and their trigger-happy posture was summed up in the colloquial refrain: "Take another step and we'll let you have it."

Near dawn on 13 June 1938, a Manchurian patrol detected a suspicious figure in the fog swirling over Changlingtzu Hill on the Siberian–Manchurian frontier. Challenged at 15 feet, the suspect hurled two pistols to the ground and raised his hands in surrender. At headquarters, the police soon realized this was no routine border-trespassing case. The man was a defector and he was a Russian general, in fact he was the director of all NKVD forces in the Soviet Far East. Beneath a mufti of spring coat and hunting cap, he wore a full uniform with medals. His identification card No. 83 designated him as G. S. Lyushkov, Commissar 3rd Class, countersigned by Nikolai Yezhov, NKVD head in Moscow. Lyushkov was promptly turned over to the Japanese military authorities, who transferred him to Seoul and then to Tokyo under close escort. On 1 July, the Japanese press was permitted to disclose that Lyushkov had sought refuge in Japan. Ten days later, to capitalize on the commissar's notoriety and to confound skeptics, the Japanese produced Lyushkov at a press conference in Tokyo. For the Japanese and foreign correspondents, who met separately with him, Lyushkov described Soviet Far East strength and the turmoil wracking the USSR, because for those of you unfamiliar this was during the Stalinist purges. Clearly, the Japanese had gained a unique reservoir of high-level intelligence and a wealth of materials, including notes scratched in blood by suspects incarcerated at Khabarovsk.

A general tightening of Russian frontier security had recently been reported. Natives of Fangchuanting asserted that a Soviet cavalry patrol appeared in June, seemingly for the first time. Contact with Yangkuanping, northwest of Khasan, was severed. More importantly, Japanese Army Signal Corps intelligence detected a surge of Soviet message traffic from the Posyet Bay district. After Lyushkov's defection, a drastic reshuffle in the local Russian command apparently occurred, and responsibility for border surveillance seems to have been reallocated. Japanese records indicate that the Novokievsk security force commander was relieved and the sector garrison replaced by troops from Vladivostok. Gaimusho intelligence also received reports that a border garrison unit had been transferred from Khabarovsk or Chita to the Tumen sector.

The Kwantung Army signal monitors also intercepted two significant frontline messages on 6 July from the new Russian local commander in the Posyet region, addressed to Lieutenant General Sokolov in Khabarovsk. Decoded, the messages suggested

(1) that ammunition for infantry mortars amounted to less than half the required supply; and

(2) a recommendation that higher headquarters authorize Russian elements to secure certain unoccupied high ground west of Khasan.

The commander noted terrain advantages and the contemplated construction of emplacements that would command Najin and the Korean railway. As a start, at least one Russian platoon should be authorized to dig in on the highest ground (presumably Changkufeng) and deploy four tons of entanglements to stake out the Soviet claim. Korea Army Headquarters received a telegram from the Kwantung Army on 7 July conveying the deciphered messages. On the same day, the 19th Division in North Korea telephoned Seoul that, on 6 July, three or four Soviet horsemen had been observed reconnoitering Manchurian territory from atop a hill called Changkufeng. The alarming intelligence from the Kwantung Army and the front warranted immediate attention by the Korea Army. Some Kwantung Army officers doubted the significance of the developments, with one intelligence official even suggesting the Russian messages might be a deliberate ploy designed to entrap the Japanese at Changkufeng.

On 7–8 July, all staff officers in Seoul convened at army headquarters. The name of Changkufeng Hill was not well known, but maps and other data suggested that neither the Japanese nor the Russians had previously stationed border units in the ridge complex west of Khasan. As early as March 1936, Army Commander Koiso Kuniaki had distributed maps to subordinate units, indicating which sectors were in dispute. No patrol was to enter zones lacking definitive demarcation. Until then, the only Japanese element east of the Tumen was a Manchurian policeman at Fangchuanting. Ownership of the high ground emerged as an early issue. A number of other points were raised by the Kwantung Army:

1. At present, Soviet elements in the area were negligible.

2. The intrusion must not be overlooked. The Russians could be expected to exploit any weakness, and half-measures would not suffice, especially regarding the Japanese defense mission along a 125-mile frontier.

3. In Japanese hands, Changkufeng Hill would be useful, but two excellent observation posts already existed in the neighboring sector of the Manchurian tongue.

4. With dissidence and purges underway, the Russians may have judged it necessary to seal border gaps, particularly after Lyushkov's defection. They may also have sought to control Changkufeng to offset Japanese dominance of the high ground to the north.

5. Soviet seizure of Changkufeng would upset the delicate status quo and could provoke a contest for equivalent observation posts.

6. In broader terms, it mattered little whether the Russians sought a permanent observation post on Changkufeng Hill, which was of relatively minor strategic value. Japan's primary concern lay in the China theater; Changkufeng was peripheral. The Japanese should not expend limited resources or become distracted.

7. The matter required consultation with the high command in Tokyo.

In the absence of more comprehensive intelligence, the assembled staff officers concluded that the Korea Army should, at a minimum, ignore or disregard Soviet actions for the time being, while maintaining vigilant observation of the area. The consensus was communicated to Major General Kitano Kenzo, the Korea Army chief of staff, who concurred, and to Koiso. Upon learning that the recommendation advocated a low posture, Koiso inquired only whether the opinion reflected the unanimous view of the staff. Having been assured that it did, he approved the policy. Koiso, then 58, was at the threshold of the routine personnel changes occurring around 15 July. He had just been informed that he would retire and that General Nakamura Kotaro would succeed him. Those acquainted with Koiso perceived him as treating the border difficulties as a minor anticlimax in the course of his command tour. He appeared unemphatic or relaxed as he prepared to depart from a post he had held for twenty-one years. Although neither Koiso nor his staff welcomed the Soviet activities that appeared under way, his reaction likely reflected a reluctance to make decisions that could constrain his soon-to-arrive successor.

On 8 July Koiso authorized the dispatch of warnings to the 19th Division at Nanam, to the Hunchun garrison, and to the intelligence branch at Hunchun. These units were instructed to exercise maximum precautions and to tighten frontier security north of Shuiliufeng. In response to the initial appearance of Soviet horsemen at Changkufeng, the Kucheng Border Garrison Unit of the 76th Infantry Regiment maintained close surveillance across the Tumen. By about noon on 9 July, patrols detected approximately a dozen Russian troops commencing construction atop Changkufeng. Between 11 and 13 July, the number of soldiers on the slopes increased to forty; there were also thirty horses and eleven camouflaged tents. Operating in shifts on the western side, thirty meters from the crest, the Russians erected barbed wire and firing trenches; fifty meters forward, they excavated observation trenches. In addition to existing telephone lines between Changkufeng, Lake Khasan, and Kozando, the Russians installed a portable telephone net. Logistical support was provided by three boats on the lake. Approximately twenty kilometers to the east, well within Soviet territory, large forces were being mobilized, and steamship traffic into Posyet Bay intensified. Upon learning of the "intrusion" at Changkufeng on 9 July, Lt. General Suetaka Kamezo, the commander of the 19th Division, dispatched staff officers to the front and prepared to send elements to reinforce border units.

The special significance of Suetaka and his division stemmed from a series of unusual circumstances. Chientao Province, the same zone into which Lyushkov had fled and the sector where Soviet horsemen had appeared, fell within Manchukuo geographically and administratively. Yet, in terms of defense, the configuration of the frontier, the terrain, and the transportation network more closely connected the region with North Korea than with southeastern Manchuria. Approximately 80% of the population was of Korean origin, which implied Japanese rather than Manchukuoan allegiance. Consequently, the Korea Army had been made operationally responsible for the defense of Chientao and controlled not only the three-battalion garrison at Hunchun but also the intelligence detachment located there. In the event of war, the Korea Army's mission was defined as mobilization and execution of subsidiary operational tasks against the USSR, under the control and in support of the Kwantung Army.

The Korea Army ordinarily possessed two infantry divisions, the 19th in North Korea and the 20th stationed at Seoul, but the 20th Division had already departed for China, leaving only the 20th Depot Division in the capital. Beyond sparse ground units, devoid of armor and with weak heavy artillery, there were only two air regiments in Korea, the nearest being the unit at Hoeryong. The Korea Army was designed to maintain public security within Korea as well as fulfill minimal defensive responsibilities. Such an army did not require a full-time operations officer, and none was maintained. When needed, as in mid-1938, the task fell to the senior staff officer, in this case Colonel Iwasaki Tamio. In peacetime, training constituted the primary focus.

Thus, the 19th Division was entrusted with defending northeastern Korea. Its commander, Suetaka, a seasoned infantryman, resented the fact that his elite force had never engaged in combat in China. He intensified training with zeal, emphasizing strict discipline, bravery, aggressiveness, and thorough preparation. Japanese veterans characterized him as severe, bullish, short-tempered, hot-blooded, highly strung, unbending, and stubborn. Nonetheless, there was widespread respect for his realistic training program, maintained under firm, even violent, personal supervision. His men regarded Suetaka as a professional, a modern samurai who forged the division into superb condition. Privately, he was reputed for sensitivity and warmth; a Japanese phrase "yakamashii oyaji" captures the dual sense of stern father and martinet in his character.

At the outset, however, Suetaka displayed little aggression. Although not widely known, he did not welcome the orders from army headquarters to deploy to the Tumen. Until late July, he remained somewhat opposed to the notion of dislodging the Soviets from the crest, a proposition arising from neither the division staff nor, initially, Suetaka himself. Colonel Sato noted that, for a week after reports of Soviet excavation at Changkufeng, the division's response was limited to preparations for a possible emergency, as they perceived the matter as a local issue best settled through diplomacy.

Korea Army officers acknowledged that, around the time the Soviets consolidated their outpost strength at Changkufeng, an informal and personal telegram arrived in Seoul from a Kwantung Army Intelligence field-grade officer who specialized in Soviet affairs. If the Korea Army hesitated, the Kwantung Army would be obliged to eject the Russians; the matter could not be ignored. While the telegram did not demand a reply and struck several officers as presumptuous and implausible, the message was promptly shown to Koiso. Koiso was driven to immediate action, he wired Tokyo asserting that only the Korea Army could and would handle the incident. One staff officer recalled "We felt we had to act, out of a sense of responsibility. But we resented the Kwantung Army's interference." The Korea Army staff convened shortly after receipt of the unofficial telegram from Hsinking. Based on the latest intelligence from the division dated 13 July, the officers prepared an assessment for submission to the army commander. The hypotheses were distilled into three scenarios:

1. The USSR, or the Far East authorities, desires hostilities. Conclusion: Slightly possible.

2. The USSR seeks to restrain Japan on the eve of the pivotal operations in China: the major Japanese offensive to seize Hankow. Conclusion: Highly probable.

3. The Posyet district commander is new in his post; by occupying the Changkufeng ridges, he would demonstrate loyalty, impress superiors, and seek glory. Conclusion: Possible.

Late on 13 July or early on 14 July, Koiso approved the dispatch of a message to the vice minister of war, and the Kwantung Army chief of staff:

"Lake Khasan area lies in troublesome sector USSR has been claiming . . . in accordance with treaties [said Secret Message No. 913], but we interpret it to be Manchukuoan territory, evident even from maps published by Soviet side. Russian actions are patently illegal, but, considering that area does not exert major or immediate influence on operations [Japan] is intending and that China Incident is in full swing, we are not going to conduct counterattack measures immediately. This army is thinking of reasoning with Soviets and requesting pullback, directly on spot. . . . In case Russians do not accede in long run, we have intention to drive Soviet soldiers out of area east of Khasan firmly by use of force." The message concluded with a request that the Tokyo authorities lodge a formal protest with the USSR, on behalf of Manchukuo and Japan, and guide matters so that the Russians would withdraw quickly.

Dominant in Japanese high command thinking in 1938 was the China theater; the Changkufeng episode constituted a mere digression. A sequence of Japanese tactical victories had preceded the summer: Tsingtao fell in January; the Yellow River was reached in March; a "reformed government of the Republic of China" was installed at Nanking several weeks later; Amoy fell in early May; Suchow fell on the 20th. With these gains, northern and central fronts could be linked by the Japanese. Yet Chinese resistance persisted, and while public statements anticipated imminent Chinese dissension, private admissions acknowledged that the partial effects of Suchow's fall were ominous: control might pass from Chiang Kai-shek to the Communists, Chinese defiance might intensify, and Soviet involvement could ensue. A Hankow drive appeared desirable to symbolize the conclusion of the military phase of hostilities. The Japanese and their adversaries were in accord regarding the importance of the summer and autumn campaigns. Even after Suchow's fall, the government discouraged public insinuations that enemy resistance was collapsing; when Chiang addressed the nation on the first anniversary of hostilities, Premier Konoe prophetically proclaimed, "The war has just begun."

Colonel Inada Masazum served as the Army General Staff's principal figure for the Changkufeng affair, occupying the position of chief of the 2nd Operations Section within the Operations Bureau in March 1938. A distinguished graduate of the Military Academy, Inada completed the War College program and held a combination of line, instructional, and staff assignments at the War College, the Army General Staff, and the War Ministry. He was recognized as a sharp, highly capable, and driveful personality, though some regarded him as enigmatic. Following the capture of Suchow, Imperial General Headquarters on 18 June ordered field forces to undertake operational preparations for a drive to seize the Wuhan complex. Inada favored a decisive move aimed at achieving a rapid political settlement. He acknowledged that Soviet intervention in 1938, during Japan's involvement in China, would have been critical. Although Japanese forces could still defeat the Chinese, an overextended Japanese Army might be fatally compromised against the Russians. Soviet assistance to China was already pronouncedly unwelcome. The Soviets were reported to possess roughly 20 rifle divisions, four to five cavalry divisions, 1,500 tanks, and 1,560 aircraft, including 300 bombers with a range of approximately 3,000 kilometers, enabling reach from Vladivostok to Tokyo. Soviet manpower in Siberia was likely near 370,000. In response, Japanese central authorities stressed a no-trouble policy toward the USSR while seeking to "wall off" the border and bolster the Kwantung Army as quickly as possible. Nevertheless, the envisaged correction of the strategic imbalance could not occur before 1943, given shortages in ammunition, manpower, and materiel across existing theaters in China. By the end of 1937 Japan had committed 16 of its 24 divisions to China, bringing the standing force to roughly 700,000. Army General Staff planners reallocated three ground divisions, intended for a northern contingency, from north to central China, even as the Kwantung Army operated from a less favorable posture.

Attitudes toward the northern problem varied within senior military circles. While concern persisted, it was not universal. As campaigns in China widened, planning at the high command level deteriorated, propagating confusion and anxiety to field armies in China. The Japanese Navy suspected that the Army general staff was invoking the USSR as a pretext for broader strategic aims—namely, to provoke a more consequential confrontation with the USSR while the Navy contended with its own strategic rivalries with the Army, centered on the United States and Britain. Army leaders, however, denied aggressive intent against the USSR at that time. The Hankow plan encountered substantial internal opposition at high levels. Private assessments among army planners suggested that a two-front war would be premature given operational readiness and troop strength. Not only were new War Ministry officials cautious, but many high-ranking Army general staff officers and court circles shared doubts.

Aggressive tendencies, influenced by subordinates and the Kwantung Army, were evident in Inada, who repeatedly pressed Tada Shun, the deputy army chief of staff, to endorse the Wuhan drive as both necessary and feasible, arguing that the USSR would gain from Japan's weakening without incurring substantial losses. Inada contended that Stalin was rational and that time favored the USSR in the Far East, where industrial buildup and military modernization were ongoing. He argued that the Soviet purges impeded opportunistic ventures with Japan. He posited that Nazi Germany posed a growing threat on the western front, and thus the USSR should be avoided by both Japan, due to China and Russia, due to Germany. While most of the army remained engaged in China, Tada did not initially share Inada's views; only after inspecting the Manchurian borders in April 1938 did he finally align with Inada's broader vision, which encompassed both northern and Chinese considerations. During this period, Inada studied daily intelligence from the Kwantung Army, and after Lyushkov's defection in June, reports suggested the Soviets were following their sector commander's recommendations. Russian troops appeared at Changkufeng, seemingly prepared to dig in. Inada recollects his reaction: "That's nice, my chance has come."

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The simmering Soviet–Japanese border clashes centered on Changkufeng Hill near Lake Khanka, set within a broader history of contested frontiers dating to Qing and Tsarist treaties. Japan, prioritizing China, considered Changkufeng peripheral but ready to confront Soviet encroachment; Moscow aimed to consolidate border gains, with high-level war planning overlaying regional skirmishes. Conflict loomed over Manchuria.