3.190 Fall and Rise of China: Zhukov Unleashes Tanks at Nomonhan

Last time we spoke about General Zhukov's arrival to the Nomohan incident. The Kwantung Army's inexperienced 23rd Division, under General Komatsubara, suffered heavy losses in failed offensives, including Colonel Yamagata's assault and the annihilation of Lieutenant Colonel Azuma's detachment, resulting in around 500 Japanese casualties. Tensions within the Japanese command intensified as Kwantung defied Tokyo's restraint, issuing aggressive orders like 1488 and launching a June 27 air raid on Soviet bases, destroying dozens of aircraft and securing temporary air superiority. This provoked Moscow's fury and rebukes from Emperor Hirohito. On June 1, Georgy Zhukov, a rising Red Army tactician and tank expert, was summoned from Minsk. Arriving June 5, he assessed the 57th Corps as inadequate, relieved Commander Feklenko, and took charge of the redesignated 1st Army Group. Reinforcements included mechanized brigades, tanks, and aircraft. Japanese intelligence misread Soviet supply convoys as retreats, underestimating Zhukov's 12,500 troops against their 15,000. By July, both sides poised for a massive clash, fueled by miscalculations and gekokujo defiance.

#190 Zhukov Unleashes Tanks at Nomohan

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At 4:00 a.m. on July 1, 15,000 heavily laden Japanese troops began marching to their final assembly and jump-off points. The sun rose at 4:00 a.m. and set at 9:00 p.m. that day, but the Japanese advance went undetected by Soviet/MPR commanders, partly because the June 27 air raid had temporarily cleared Soviet reconnaissance from the skies. On the night of July 1, Komatsubara launched the first phase. The 23rd Division, with the Yasuoka Detachment, converged on Fui Heights, east of the Halha River, about eleven miles north of its confluence with the Holsten. The term "heights" is misleading here; a Japanese infantry colonel described Fui as a "raised pancake" roughly one to one-and-a-half miles across, about thirty to forty feet higher than the surrounding terrain. For reasons not fully explained, the small Soviet force stationed on the heights was withdrawn during the day on July 1, and that night Fui Heights was occupied by Komatsubara's forces almost unopposed. This caused little stir at Zhukov's headquarters. Komatsubara bided his time on July 2.

On the night of July 2–3, the Japanese achieved a brilliant tactical success. A battalion of the 71st Infantry Regiment silently crossed the Halha River on a moonless night and landed unopposed on the west bank opposite Fui Heights. Recent rains had swollen the river to 100–150 yards wide and six feet deep, making crossing difficult for men, horses, or vehicles. Combat engineers swiftly laid a pontoon bridge, completing it by 6:30 a.m. on July 3. The main body of Komatsubara's 71st and 72nd Infantry Regiments (23rd Division) and the 26th Regiment (7th Division) began a slow, arduous crossing. The pontoon bridge, less than eight feet wide, was a bottleneck, allowing only one truck at a time. The attackers could not cross with armored vehicles, but they did bring across their regimental artillery, 18 x 37-mm antitank guns, 12 x 75-mm mountain guns, 8 x 75-mm field guns, and 4 x 120-mm howitzers, disassembled, packed on pack animals, and reassembled on the west bank. The crossing took the entire day, and the Japanese were fortunate to go without interception.

The Halha crossing was commanded personally by General Komatsubara and was supported by a small Kwantung Army contingent, including General Yano (deputy chief of staff), Colonel Hattori, and Major Tsuji from the Operations Section. Despite the big air raid having alerted Zhukov, the initial Japanese moves from July 1–3 achieved complete tactical surprise, aided by Tsuji's bold plan. The first indication of the major offensive came when General Yasuoka's tanks attacked predawn on July 3. Yasuoka suspected Soviet troops south of him attempting to retreat across the Halha to the west bank, and he ordered his tanks to attack immediately, with infantry not yet in position. The night's low clouds, no moon, and low visibility—along with a passing thunderstorm lighting the sky—made the scene dramatic. Seventy Japanese tanks roared forward, supported by infantry and artillery, and the Soviet 149th Infantry Regiment found itself overwhelmed.

Zhukov, hearing of Yasuoka's assault but unaware that Komatsubara had crossed the Halha, ordered his armor to move northeast to Bain Tsagan to confront the initiative. There, Soviet armor clashed with Japanese forces in a chaotic, largely uncoordinated engagement. The Soviet counterattacks, supported by heavy artillery, halted much of the Japanese momentum, and by late afternoon Japanese infantry had to dig in west of the Halha. The crossing had been accomplished without Soviet reconnaissance detecting it in time, but Zhukov's counterattacks, the limits of Japanese armored mobility across the pontoon, and the heat and exhaustion of the troops constrained the Japanese effort. By the afternoon of July 3, Zhukov's forces were pressing hard, and the Japanese momentum began to stall.

Yasuoka's tanks, supported by a lack of infantry and the fatigue and losses suffered by the infantry, could not close the gap to link with Komatsubara's forces. The Type 89 tanks, designed for infantry support, were ill-suited to penetrating Soviet armor, especially when faced with BT-5/BT-7 tanks and strong anti-tank guns. The Type 95 light tanks were faster but lightly armored, and suffered heavily from Soviet fire and air attacks. Infantry on the western bank struggled to catch up with tanks, shot through by Soviet artillery and armor, while the 64th Regiment could not keep pace with the tanks due to the infantry's lack of motorized transport. By late afternoon, Yasuoka's advance stalled far short of the river junction and the Soviet bridge. The infantry dug in to withstand Soviet bombardment, and the Japanese tank regiments withdrew to their jump-off points by nightfall. The Japanese suffered heavy losses in tanks, though some were recovered and repaired; by July 9, KwAHQ decided to withdraw its two tank regiments from the theater. Armor would play no further role in the Nomonhan conflict. The Soviets, by contrast, sustained heavier tank losses but began to replenish with new models. The July offensive, for Kwantung Army, proved a failure.

Part of the failure stemmed from a difficult blend of terrain and logistics. Unusually heavy rains in late June had transformed the dirt roads between Hailar and Nomonhan into a mud-filled quagmire. Japanese truck transport, already limited, was so hampered by these conditions that combat effectiveness suffered significantly. Colonel Yamagata's 64th Infantry Regiment, proceeding on foot, could not keep pace with or support General Yasuoka's tanks on July 3–4. Komatsubara's infantry on the west bank of the Halha ran short of ammunition, food, and water. As in the May 28 battle, the main cause of the Kwantung Army's July offensive failure was wholly inadequate military intelligence. Once again, the enemy's strength had been seriously underestimated. Moreover, a troubling realization was dawning at KwAHQ and in the field: the intelligence error was not merely quantitative but qualitative. The Soviets were not only more numerous but also far more potent than anticipated. The attacking Japanese forces initially held a slight numerical edge and enjoyed tactical surprise, but the Red Army fought tenaciously, and the weight of Soviet firepower proved decisive.

Japan, hampered by a relative lack of raw materials and industrial capacity, could not match the great powers in the quantitative production of military materiel. Consequently, Japanese military leaders traditionally emphasized the spiritual superiority of Japan's armed forces in doctrine and training, often underestimating the importance of material factors, including firepower. This was especially true of the army that had carried the tactic of the massed bayonet charge into World War II. This "spiritual" combat doctrine arose from necessity; admitting material superiority would have implied defeat. Japan's earlier victories in the Sino-Japanese War, Russo-Japanese War, the Manchurian incident, and the China War, along with legendary medieval victories over the Mongol hordes, seemed to confirm the transcendent importance of fighting spirit. Only within such a doctrine could the Imperial Japanese Army muster inner strength and confidence to face formidable enemies. This was especially evident against Soviet Russia, whose vast geography, population, and resources loomed large. Yet what of its spirit? The Japanese military dismissed Bolshevism as a base, materialist philosophy utterly lacking spiritual power. Consequently, the Red Army was presumed to have low morale and weak fighting effectiveness. Stalin's purges only reinforced this belief.

Kwantung Army's recent experiences at Nomonhan undermined this outlook. Among ordinary soldiers and officers alike, from the 23rd Division Staff to KwAHQ—grim questions formed: Had Soviet materiel and firepower proven superior to Japanese fighting spirit? If not, did the enemy possess a fighting spirit comparable to their own? To some in Kwantung Army, these questions were grotesque and almost unthinkable. To others, the implications were too painful to face. Perhaps May and July's combat results were an aberration caused by the 23rd Division's inexperience. Nevertheless, a belief took hold at KwAHQ that this situation required radical rectification. Zhukov's 1st Army Headquarters, evaluating recent events, was not immune to self-criticism and concern for the future. The enemy's success in transporting nearly 10,000 men across the Halha without detection—despite heightened Soviet alert after the June 27 air raid—revealed a level of carelessness and lack of foresight at Zhukov's level. Zhukov, however, did not fully capitalize on Komatsubara's precarious position on July 4–5.

Conversely, Zhukov and his troops reacted calmly in the crisis's early hours. Although surprised and outnumbered, Zhukov immediately recognized that "our trump cards were the armored detachments, and we decided to use them immediately." He acted decisively, and the rapid deployment of armor proved pivotal. Some criticized the uncoordinated and clumsy Soviet assault on Komatsubara's infantry on July 3, but the Japanese were only a few hours' march from the river junction and the Soviet bridge. By hurling tanks at Komatsubara's advance with insufficient infantry support, Mikhail Yakovlev (11th Tank Brigade) and A. L. Lesovoi (7th Mechanized Brigade) incurred heavy losses. Nonetheless, they halted the Japanese southward advance, forcing Komatsubara onto the defensive, from which he never regained momentum. Zhukov did not flinch from heavy casualties to achieve his objectives. He later told General Dwight D. Eisenhower that if the enemy faced a minefield, their infantry attacked as if it did not exist, treating personnel mine losses as equal to those that would have occurred if the Germans defended the area with strong troops rather than minefields. Zhukov admitted losing 120 tanks and armored cars that day—a high price, but necessary to avert defeat.

Years later, Zhukov defended his Nomonhan tactics, arguing he knew his armor would suffer heavy losses, but that was the only way to prevent the Japanese from seizing the bridge at the river confluence. Had Komatsubara's forces advanced unchecked for another two or three hours, they might have fought through to the Soviet bridge and linked with the Yasuoka detachment, endangering Zhukov's forces. Zhukov credited Yakovlev, Lesovoi, and their men with stabilizing the crisis through timely and self-sacrificing counterattacks. The armored car battalion of the 8th MPR Cavalry Division also distinguished itself in this action. Zhukov and his tankmen learned valuable lessons in those two days of brutal combat. A key takeaway was the successful use of large tank formations as an independent primary attack force, contrary to then-orthodox doctrine, which saw armor mainly as infantry support and favored integrating armor into every infantry regiment rather than maintaining large, autonomous armored units. The German blitzkrieg demonstrations in Poland and Western Europe soon followed, but, until then, few major armies had absorbed the tank-warfare theories championed by Basil Liddell-Hart and Charles de Gaulle. The Soviet high command's leading proponent of large-scale tank warfare had been Marshal Mikhail Tukhachevsky. His execution in 1937 erased those ideas, and the Red Army subsequently disbanded armored divisions and dispersed tanks among infantry, misapplying battlefield lessons from the Spanish Civil War.

Yet Zhukov was learning a different lesson on a different battlefield. The open terrain of eastern Mongolia favored tanks, and Zhukov was a rapid learner. The Russians also learned mundane, but crucial, lessons: Japanese infantry bravely clambering onto their vehicles taught Soviet tank crews to lock hatch lids from the inside. The BT-5 and BT-7 tanks were easily set aflame by primitive hand-thrown firebombs, and rear deck ventilation grills and exhaust manifolds were vulnerable and required shielding. Broadly, the battle suggested to future Red Army commander Zhukov that tank and motorized troops, coordinated with air power and mobile artillery, could decisively conduct rapid operations. Zhukov was not the first to envision combining mobile firepower with air and artillery, but he had rare opportunities to apply this formula in crucial tests. The July offensive confirmed to the Soviets that the Nomonhan incident was far from a border skirmish; it signaled intent for further aggression. Moscow's leadership, informed by Richard Sorge's Tokyo network, perceived Japan's renewed effort to draw Germany into an anti-Soviet alliance as a dangerous possibility. Stalin and Vyacheslav Molotov began indicating to Joachim von Ribbentrop and Adolf Hitler that Berlin's stance on the Soviet–Japanese conflict would influence Soviet-German rapprochement considerations.

Meanwhile, Moscow decided to reinforce Zhukov. Tens of thousands of troops and machines were ordered to Mongolia, with imports from European Russia. Foreign diplomats traveling the Trans-Siberian Railway reported eastbound trains jammed with personnel and matériel. The buildup faced a major bottleneck at Borzya, the easternmost railhead in the MPR, about 400 miles from the Halha. To prevent a logistics choke, a massive truck transport operation was needed. Thousands of trucks, half-tracks, gun-towing tractors, and other vehicles were organized into a continuous eight-hundred-mile, five-day shuttle run. The Trans-Baikal Military District, under General Shtern, supervised the effort. East of the Halha, many Japanese officers still refused to accept a failure verdict for the July offensive. General Komatsubara did not return to Hailar, instead establishing a temporary divisional HQ at Kanchuerhmiao, where his staff grappled with overcoming Soviet firepower. They concluded that night combat—long a staple of Japanese infantry tactics—could offset Soviet advantages. On July 7 at 9:30 p.m., a thirty-minute Japanese artillery barrage preceded a nighttime assault by elements of the 64th and 72nd Regiments. The Soviet 149th Infantry Regiment and supporting Mongolian cavalry were surprised and forced to fall back toward the Halha before counterattacking. Reinforcements arrived on both sides, and in brutal close-quarters combat the Japanese gained a partial local advantage, but were eventually pushed back; Major I. M. Remizov of the 149th Regiment was killed and later posthumously named a Hero of the Soviet Union.

Since late May, Soviet engineers had built at least seven bridges across the Halha and Holsten Rivers to support operations. By July 7–8, Japanese demolition teams destroyed two Soviet bridges. Komatsubara believed that destroying bridges could disrupt Soviet operations east of the Halha and help secure the border. Night attacks continued from July 8 to July 12 against the Soviet perimeter, with Japanese assaults constricting Zhukov's bridgehead while Soviet artillery and counterattacks relentlessly pressed. Casualties mounted on both sides. The Japanese suffered heavy losses but gained some positions; Soviet artillery, supported by motorized infantry and armor, gradually pushed back the attackers. The biggest problem for Japan remained Soviet artillery superiority and the lack of a commensurate counter-battery capability. Japanese infantry had to withdraw to higher ground at night to avoid daytime exposure to artillery and tanks.

On the nights of July 11–12, Yamagata's 64th Regiment and elements of Colonel Sakai Mikio's 72nd Regiment attempted a major assault on the Soviet bridgehead. Despite taking heavy casualties, the Japanese managed to push defenders back to the river on occasion, but Soviet counterattacks, supported by tiresome artillery and armor, prevented a decisive breakthrough. Brigade Commander Yakovlev of the 11th Armored, who led several counterattacks, was killed and later honored as a Hero of the Soviet Union; his gun stands today as a monument at the battlefield. The July 11–12 action marked the high-water mark of the Kwantung Army's attempt to expel Soviet/MPR forces east of the Halha. Komatsubara eventually suspended the costly night attacks; by that night, the 64th Regiment had suffered roughly 80–90 killed and about three times that number wounded. The decision proved controversial, with some arguing that he had not realized how close his forces had come to seizing the bridge. Others argued that broader strategic considerations justified the pause.

Throughout the Nomonhan fighting, Soviet artillery superiority, both quantitative and qualitative, became painfully evident. The Soviet guns exacted heavy tolls and repeatedly forced Japanese infantry to withdraw from exposed positions. The Japanese artillery, in contrast, could not match the Red Army's scale. By July 25, Kwantung Army ended its artillery attack, a humiliating setback. Tokyo and Hsinking recognized the futility of achieving a decisive military victory at Nomonhan and shifted toward seeking a diplomatic settlement, even if concessions to the Soviet Union and the MPR were necessary. Kwantung Army, however, opposed negotiations, fearing it would echo the "Changkufeng debacle" and be read by enemies as weakness. Tsuji lamented that Kwantung Army's insistence on framing the second phase as a tie—despite heavy Soviet losses, revealed a reluctance to concede any territory.

Differences in outlook and policy between AGS and Kwantung Army—and the central army's inability to impose its will on Manchukuo's field forces—became clear. The military establishment buzzed with stories of gekokujo (the superiority of the superior) within Kwantung Army and its relations with the General Staff. To enforce compliance, AGS ordered General Isogai to Tokyo for briefings, and KwAHQ's leadership occasionally distanced itself from AGS. On July 20, Isogai arrived at General Staff Headquarters and was presented with "Essentials for Settlement of the Nomonhan Incident," a formal document outlining a step-by-step plan for Kwantung Army to maintain its defensive position east of the Halha while diplomatic negotiations proceeded. If negotiations failed, Kwantung Army would withdraw to the boundary claimed by the Soviet Union by winter.

Isogai, the most restrained member of the Kwantung Army circle, argued against accepting the Essentials, insisting on preserving Kwantung Army's honor and rejecting a unilateral east-bank withdrawal. A tense exchange followed, but General Nakajima ended the dispute by noting that international boundaries cannot be determined by the army alone. Isogai pledged to report the General Staff's views to his commander and take the Essentials back to KwAHQ for study. Technically, the General Staff's Essentials were not orders; in practice, however, they were treated as such. Kwantung Army tended to view them as suggestions and retained discretion in implementation. AGS hoped the Essentials would mollify Kwantung Army's wounded pride. The August 4 decision to create a 6 Army within Kwantung Army, led by General Ogisu Rippei, further complicated the command structure. Komatsubara's 23rd Division and nearby units were attached to the 6 Army, which also took responsibility for defending west-central Manchukuo, including the Nomonhan area. The 6 Army existed largely on paper, essentially a small headquarters to insulate KwAHQ from battlefield realities. AGS sought a more accountable layer of command between KwAHQ and the combat zone, but General Ueda and KwAHQ resented the move and offered little cooperation. In the final weeks before the last battles, General Ogisu and his small staff had limited influence on Nomonhan.

Meanwhile, the European crisis over German demands on Poland intensified, moving into a configuration highly favorable to the Soviet Union. By the first week of August, it became evident in the Kremlin that both Anglo-French powers and the Germans were vying to secure an alliance with Moscow. Stalin knew now that he would likely have a free hand in the coming war in the West. At the same time, Richard Sorge, the Soviet master spy in Tokyo, correctly reported that Japan's top political and military leaders sought to prevent the escalation of the Nomonhan incident into an all-out war. These developments gave the cautious Soviet dictator the confidence to commit the Red Army to large-scale combat operations in eastern Mongolia. In early August, Stalin ordered preparations for a major offensive to clear the Nomonhan area of the "Japanese samurai who had violated the territory of the friendly Outer Mongolian people."

The buildup of Zhukov's 1st Army Group accelerated still further. Its July strength was augmented by the 57th and 82nd Infantry Divisions, the 6th Tank Brigade, the 212th Airborne Brigade, numerous smaller infantry, armor, and artillery units, and two Mongolian cavalry divisions. Soviet air power in the area was also greatly strengthened. When this buildup was completed by mid-August, Zhukov commanded an infantry force equivalent to four divisions, supported by two cavalry divisions, 216 artillery pieces, 498 armored vehicles, and 581 aircraft. To bring in the supplies necessary for this force to launch an offensive, General Shtern's Trans-Baikal Military District Headquarters amassed a fleet of more than 4,200 vehicles, which trucked in about 55,000 tons of materiel from the distant railway depot at Borzya.

The Japanese intelligence network in Outer Mongolia was weak, a problem that went unremedied throughout the Nomonhan incident. This deficiency, coupled with the curtailment of Kwantung Army's transborder air operations, helps explain why the Japanese remained ignorant of the scope of Zhukov's buildup. They were aware that some reinforcements were flowing eastward across the Trans-Siberian Railway toward the MPR but had no idea of the volume. Then, at the end of July, Kwantung Army Intelligence intercepted part of a Soviet telegraph transmission indicating that preparations were under way for some offensive operation in the middle of August. This caused a stir at KwAHQ. Generals Ueda and Yano suspected that the enemy planned to strike across the Halha River. Ueda's initial reaction was to reinforce the 23rd Division at Nomonhan with the rest of the highly regarded 7th Division. However, the 7th Division was Kwantung Army's sole strategic reserve, and the Operations Section was reluctant to commit it to extreme western Manchukuo, fearing mobilization of Soviet forces in the Maritime Province and a possible attack in the east near Changkufeng. The Kwantung Army commander again ignored his own better judgment and accepted the Operations Section's recommendation. The main strength of the 7th Division remained at its base near Tsitsihar, but another infantry regiment, the 28th, was dispatched to the Nomonhan area, as was an infantry battalion from the Mukden Garrison.

Earlier, in mid-July, Kwantung Army had sent Komatsubara 1,160 individual replacements to make up for casualties from earlier fighting. All these reinforcements combined, however, did little more than replace losses: as of July 25, 1,400 killed (including 200 officers) and 3,000 wounded. Kwantung Army directed Komatsubara to dig in, construct fortifications, and adopt a defensive posture. Colonel Numazaki, who commanded the 23rd Division's Engineer Regiment, was unhappy with the defensive line he was ordered to fortify and urged a slight pullback to more easily defensible terrain. Komatsubara, however, refused to retreat from ground his men had bled to take. He and his line officers still nourished hope of a revenge offensive. As a result, the Japanese defensive positions proved to be as weak as Numazaki feared.

As Zhukov's 1st Army Group prepared to strike, the effective Japanese strength at Nomonhan was less than 1.5 divisions. Major Tsuji and his colleagues in the Operations Section had little confidence in Kwantung Army's own Intelligence Section, which is part of the reason why Tsuji frequently conducted his own reconnaissance missions. Up to this time it was gospel in the Japanese army that the maximum range for large-scale infantry operations was 125–175 miles from a railway; anything beyond 200 miles from a railway was considered logistically impossible. Since Kwantung Army had only 800 trucks available in all of Manchukuo in 1939, the massive Soviet logistical effort involving more than 4,200 trucks was almost unimaginable to the Japanese. Consequently, the Operations Staff believed it had made the correct defensive deployments if a Soviet attack were to occur, which it doubted. If the enemy did strike at Nomonhan, it was believed that it could not marshal enough strength in that remote region to threaten the reinforced 23rd Division. Furthermore, the 7th Division, based at Tsitsihar on a major rail line, could be transported to any trouble spot on the eastern or western frontier in a few days.

KwAHQ advised Komatsubara to maintain a defensive posture and prepare to meet a possible enemy attack around August 14 or 15. At this time, Kwantung Army also maintained a secret organization codenamed Unit 731, officially the Epidemic Prevention and Water Purification Department of the Kwantung Army. Unit 731 specialized in biological and chemical warfare, with main facilities and laboratories in Harbin, including a notorious prison-laboratory complex. During the early August lull at Nomonhan, a detachment from Unit 731 infected the Halha River with bacteria of an acute cholera-like strain. There are no reports in Soviet or Japanese accounts that this attempted biological warfare had any effect. In the war's final days, Unit 731 was disbanded, Harbin facilities demolished, and most personnel fled to Japan—but not before they gassed the surviving 150 human subjects and burned their corpses. The unit's commander, Lieutenant General Ishii Shiro, kept his men secret and threatened retaliation against informers. Ishii and his senior colleagues escaped prosecution at the Tokyo War Crimes Trials by trading the results of their experiments to U.S. authorities in exchange for immunity.

The Japanese 6th Army exerted some half-hearted effort to construct defensive fortifications, but scarcity of building materials, wood had to be trucked in from far away—helped explain the lack of enthusiasm. More importantly, Japanese doctrine despised static defense and favored offense, so Kwantung Army waited to see how events would unfold. West of the Halha, Zhukov accelerated preparations. Due to tight perimeter security, few Japanese deserters, and a near-absence of civilian presence, Soviet intelligence found it hard to glean depth on Japanese defensive positions. Combat intelligence could only reveal the frontline disposition and closest mortar and artillery emplacements. Aerial reconnaissance showed photographs, but Japanese camouflage and mock-ups limited their usefulness. The new commander of the 149th Mechanized Infantry Regiment personally directed infiltration and intelligence gathering, penetrating Japanese lines on several nights and returning crucial data: Komatsubara's northern and southern flanks were held by Manchukuoan cavalry, and mobile reserves were lacking.

With this information, Zhukov crafted a plan of attack. The main Japanese strength was concentrated a few miles east of the Halha, on both banks of the Holsten River. Their infantry lacked mobility and armor, and their flanks were weak. Zhukov decided to split the 1st Army Group into three strike forces: the central force would deliver a frontal assault to pin the main Japanese strength, while the northern and southern forces, carrying the bulk of the armor, would turn the Japanese flanks and drive the enemy into a pocket to be destroyed by the three-pronged effort. The plan depended on tactical surprise and overwhelming force at the points of attack. The offensive was to begin in the latter part of August, pending final approval from Moscow.

To ensure tactical surprise, Zhukov and his staff devised an elaborate program of concealment and deception, disinformation. Units and materiel arriving at Tamsag Bulak toward the Halha were moved only at night with lights out. Noting that the Japanese were tapping telephone lines and intercepting radio messages, 1st Army Headquarters sent a series of false messages in an easily decipherable code about defensive preparations and autumn-winter campaigning. Thousands of leaflets titled "What the Infantryman Should Know about Defense" were distributed among troops. About two weeks before the attack, the Soviets brought in sound equipment to simulate tank and aircraft engines and heavy construction noises, staging long, loud performances nightly. At first, the Japanese mistook the sounds for large-scale enemy activity and fired toward the sounds. After a few nights, they realized it was only sound effects, and tried to ignore the "serenade." On the eve of the attack, the actual concentration and staging sounds went largely unnoticed by the Japanese.

On August 7–8, Zhukov conducted minor attacks to expand the Halha bridgehead to a depth of two to three miles. These attacks, contained relatively easily by Komatsubara's troops, reinforced Kwantung Army's false sense of confidence. The Japanese military attaché in Moscow misread Soviet press coverage. In early August, the attaché advised that unlike the Changkufeng incident a year earlier, Soviet press was largely ignoring the conflict, implying low morale and a favorable prognosis for the Red Army. Kwantung Army leaders seized on this as confirmation to refrain from any display of restraint or doubt, misplaced confidence.

There were, however, portents of danger. Three weeks before the Soviet attack, Colonel Isomura Takesuki, head of Kwantung Army's Intelligence Section, warned of the vulnerability of the 23rd Division's flanks. Tsuji and colleagues dismissed this, and General Kasahara Yukio of AGS also went unheeded. The "desk jockey" General Staff officers commanded little respect at KwAHQ. Around August 10, General Hata Yuzaburo, Komatsubara's successor as chief of the Special Services Agency at Harbin, warned that enemy strength in the Mongolian salient was very great and seriously underestimated at KwAHQ. Yet no decisive action followed before Zhukov's attack. Kwantung Army's inaction and unpreparedness prior to the Soviet offensive appear to reflect faulty intelligence compounded by hubris. But a more nuanced explanation suggests a fatalistic wishful thinking rooted in the Japanese military culture—the belief that their spiritual strength would prevail, leading them to assume enemy strength was not as great as reported, or that victory was inevitable regardless of resources.

Meanwhile, in the rational West, the Nazi war machine faced the Polish frontier as Adolf Hitler pressed Stalin for a nonaggression pact. The German-Soviet Nonaggression Pact would neutralize the threat of a two-front war for Germany and clear the way for Hitler's invasion of Poland. If the pact was a green light, it signaled in both directions: it would also neutralize the German threat to Russia and clear the way for Zhukov's offensive at Nomonhan. On August 18–19, Hitler pressed Stalin to receive Ribbentrop in Moscow to seal the pact. Thus, reassured in the West, Stalin dared to act boldly against Japan. Zhukov supervised final preparations for his attack. Zhukov held back forward deployments until the last minute. By August 18, he had only four infantry regiments, a machine gun brigade, and Mongolian cavalry east of the Halha. Operational security was extremely tight: a week before the attack, Soviet radio traffic in the area virtually ceased. Only Zhukov and a few key officers worked on the plan, aided by a single typist. Line officers and service chiefs received information on a need-to-know basis. The date for the attack was shared with unit commanders one to four days in advance, depending on seniority. Noncommissioned officers and ordinary soldiers learned of the offensive one day in advance and received specific orders three hours before the attack.

Heavy rain grounded Japanese aerial reconnaissance from August 17 to midday on the 19th, but on August 19 Captain Oizumi Seisho in a Japanese scout plane observed the massing of Soviet forces near the west bank of the Halha. Enemy armor and troops were advancing toward the river in dispersed formations, with no new bridges but pontoon stocks spotted near the river. Oizumi sent a warning to a frontline unit and rushed back to report. The air group dispatched additional recon planes and discovered that the Japanese garrison on Fui Heights, near the northern end of Komatsubara's line, was being encircled by Soviet armor and mechanized infantry—observed by alarmed Japanese officers on and near the heights. These late discoveries on August 19 were not reported to KwAHQ and had no effect on the 6th Army and the 23rd Division's alertness on the eve of the storm. As is common in militaries, a fatal gap persisted between those gathering intelligence and those in a position to act on it. On the night of August 19–20, under cover of darkness, the bulk of the Soviet 1st Army Group crossed the Halha into the expanded Soviet enclave on the east bank.

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By August, European diplomacy left Moscow confident in a foothold against Germany and Britain, while Sorge's intelligence indicated Japan aimed to avoid a full-blown war. Stalin ordered a major offensive to clear Nomonhan, fueling Zhukov's buildup in eastern Mongolia. Kwantung Army, hampered by limited logistics, weak intelligence, and defensive posture, faced mounting pressure.