Nomonhan: The 1939 Defeat That Foreshadowed Japan's Military Tragedies

Japan Forward

22-05-2025

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In 1939, roughly 2,000 kilometers from Japan, a border clash between Japanese-backed Manchukuo and Soviet-supported Outer Mongolia escalated into the Nomonhan Incident. Spanning four months, the conflict became the Japanese military's first true confrontation with modern, large-scale warfare since the Sino-Japanese War.
It also laid bare deep flaws within the Imperial Japanese Army. Among them were poor communication, ambiguous chains of command, and a breakdown in operational control. These cemented Nomonhan as a textbook example of strategic and institutional failure.
But the collapse of the Soviet Union in 1991 upended the long-accepted narrative. Newly declassified documents revealed several critical facts that challenged everything previously believed about the battle.
The conflict erupted on May 11, 1939, along the Khalkhin Gol. A river demarcating the disputed border between northeastern China and eastern Mongolia, it marked the heart of the territorial dispute.
What began as a minor border skirmish soon escalated into a full-scale military confrontation between Japan and the Soviet Union. Each side mobilized the equivalent of at least two divisions. An estimated 90,000 troops clashed in what later came to be known as a war without a declaration.
Border tensions between Manchukuo and Soviet-backed Mongolia were not unusual. However, Japan was already embroiled in the Second Sino-Japanese War, and Army Headquarters in Tokyo had officially adopted a non-expansion policy.
Yet the Kwantung Army, stationed in Manchukuo, defied that stance. Citing its own "Border Defense Guide" issued on April 25, 1939, it unilaterally escalated the fighting in areas with vague territorial boundaries. For decades, the Nomonhan Incident was remembered as a crushing Japanese defeat, with an estimated 18,000 to 20,000 casualties.
"Strategically, the Soviets emerged victorious," says Tomoyuki Hanada, senior research fellow at Japan's National Institute for Defense Studies. "But the ferocity of the fighting was undeniable. Technically, it was a localized conflict in the Far East. However, the scale of casualties must have left a deep impression on both sides."
Another postwar revelation was the disconnect between the Soviet General Staff and frontline commanders, who initially differed on strategic direction. Over time, Moscow enforced top-down control. By August 1939, as the Red Army prepared its decisive offensive, it had already transformed Mongolia into a de facto satellite state and stockpiled overwhelming reserves of manpower and logistics.
Soviet commander Georgy Zhukov famously assessed his adversaries:
"The soldiers were brave, but the senior officers were incompetent." Japanese soldiers battling the Soviet Army in the Nomonhan Incident, 1939 (Wikimedia Commons)
Since their victory in the 1905 Russo-Japanese War, Japan had chronically underestimated the evolving strength of Russian and later Soviet forces.
A central figure behind the Nomonhan escalation was Masanobu Tsuji, an operations staff officer in the Kwantung Army. Though only a major, Tsuji was seen as the de facto commander, known for his aggressive, uncompromising stance. He authored the "Border Defense Guide" and played a key role in pushing forward the army's unilateral military actions.
Meanwhile, senior officers at Army Headquarters in Tokyo lacked real combat experience and had little understanding of conditions on the ground. Hanada observes, "In reality, the Kwantung Army's leadership approved Tsuji's proposals. Although the central command had adopted a non-expansion policy, it effectively turned a blind eye to the Kwantung Army's unilateral actions."
In November 1939, just two months after the ceasefire, Army Headquarters formed a study committee to investigate the failures at Nomonhan. By January 1940, the committee submitted a report emphasizing the critical importance of firepower and logistics, but its recommendations were largely disregarded.
Confronted with Soviet tanks and heavy artillery, Japan's under-equipped forces resorted to close-quarters infantry assaults. Soldiers were even reported to have attacked tanks at point-blank range with gasoline-filled cider bottles, crude improvised Molotov cocktails.
"Even when we made point-blank attacks with cider bottles, they were ineffective, and our troops were left in despair," wrote Lieutenant General Michitaro Komatsubara, commander of the 23rd Division, in his diary dated August 22, 1939.
Komatsubara's division suffered catastrophic losses, with a casualty rate of 70 to 80 percent. Despite this, operations officer Masanobu Tsuji persisted in preparing for a now-fantastical "September offensive." A formal post-incident report once again stressed the urgent need to expand Japan's artillery capabilities and logistics infrastructure. (National Institute for Defense Studies)
Tsuji and several senior officers were eventually removed from their posts. However, it was the frontline commanders, some of whom had run out of ammunition and food and were forced to retreat or surrender, who bore the harshest consequences. Many were pressured by superiors to commit suicide in the wake of the defeat.
"This illustrates just how coercive the military culture had become," Hanada explains. "It laid the groundwork for the extreme spirit-first ideology that would later consume the Japanese Army."
Despite having partial intelligence on the Soviet Union's August offensive, Japan took no concrete steps to prepare. The findings of the Army's own study committee were ignored, and the country continued its march toward war with the United States and other Allied powers.
In July 1941, Tsuji was reinstated and transferred to Army Headquarters, where he once again promoted aggressive operations, including the disastrous Guadalcanal campaign. Ironically, Lt Col Haruo Onuma, who had helped compile the Nomonhan study report, was sent to Guadalcanal as a senior staff officer that September. There, he was forced to wage a brutal campaign without the very firepower and logistics he had identified as essential.
"I saw everyone get crushed by tanks like rice crackers — it was hell."
That's what this writer's great-uncle, a Nomonhan veteran, tearfully recalled to me when I was a child. He told me they couldn't even raise their heads from the trenches under the weight of the Soviet assault.
Japan's military doctrine at the time placed unwavering faith in offensive operations and hand-to-hand combat, while severely neglecting the importance of intelligence, logistics, and realism. The glorification of willpower over strategy, and the tragic waste of life that followed, would go on to define many of Japan's later campaigns in the Pacific, echoing Nomonhan with chilling familiarity.
Yet even the Soviet Union failed to immediately apply the hard-won lessons of Nomonhan. During the Winter War with Finland (November 1939-March 1940), the Red Army, despite its overwhelming numerical and material superiority, struggled against Finnish resistance. While Finland lost 10% of its territory, it continues to frame the conflict as a successful defense of the remaining 90% — a point of national pride to this day.
In the aftermath, however, the Soviet Union began a comprehensive modernization of its military.
Hanada concludes:
"The Nomonhan Incident and the Winter War were turning points for the Soviet military. They came to understand that defeating Japan in 1945 would require robust operations and logistics."
For Japan, too, Nomonhan marked a strategic turning point. In its wake, Tokyo signed the Soviet–Japanese Neutrality Pact and shifted its focus southward. Yet Japan failed to recognize that the Soviet Union was already positioning itself for a future war with Nazi Germany — a critical oversight that would shape the fate of the region in the years to come.
Author: Shoko Ikeda, The Sankei Shimbun
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