Moscow, Soviet Union · August 20, 1939

The he Soviet Union and Japan, two expansionist powers that occupied portions of the Asian main­land north of China, butted heads in the Mongo­lian border­lands as early as 1929. They had also fought a war in 1904–1905, the Russo-Japa­nese War, over influ­ence in China, Mongolia, and Man­churia, the latter country rich in coal, iron, and grains and with warm-water ports in the northeasternmost part of China.

On this date in 1939, days before the German invasion of Poland, the two nations began a massive ten-day tank battle near the Mongolian Khal­kha River (also known as Khal­khyn Gol). It was the largest tank battle the world had yet seen and arguably the first decisive battle of the Second World War. Soviet forces were commanded by a then unknown Georgy Zhukov, who, now newly promoted to general, would become in a few short years a military legend for spear­heading the Soviet assault on Nazi Ger­many and formally accepting Ger­many’s uncon­ditional surren­der in the spring of 1945. Ironically, four years after Khal­khyn Gol Zhukov was one of two Soviet generals who coor­di­nated the Soviet armies at the Battle of Kursk, which super­seded the Japanese-Soviet border clash as the largest tank battle in history.

The defeat of Japa­nese forces in the Battle of Khal­khyn Gol (known in Japan as the “No­mon­han Inci­dent”) had the most pro­found impli­ca­tions on the con­duct of World War II. Since 1937 Japan had been en­gaged in a pro­tracted, knock­down drag-out fight in China, which lay to the south of Japan’s pup­pet state of Man­chu­kuo (Man­churia). The stun­ning Soviet vic­tory, followed by a cease­fire on Septem­ber 15, 1939, and then an agree­ment between the two bel­li­ger­ents to respect the borders of Mon­go­lia and Man­chu­kuo, per­suaded expan­sionist circles in Tokyo (par­tic­u­larly the Imperial Japa­nese Navy) to look to South­east Asia, where they saw the United States, Brit­ain, and France—all of which had resource-rich but ill-defended pos­ses­sions there—as weaker oppo­nents than the Soviets on the Asian mainland.

The stra­tegic change in course for Japan, which the Battle of Khal­khyn Gol prompted, even­tually led to a change in Japan’s expan­sionist for­tunes, beginning with the attack on the Philip­pines, the Dutch East Indies (Indo­nesia), Brit­ish Malaya (Malay­sia), Singa­pore, and the Amer­i­can pos­ses­sion of Hawaii on Decem­ber 7 and 8, 1941. The strategic change in course also presaged Japan’s downfall.

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Battles of Khalkhyn Gol: The Soviet Union versus Japan, May to September 1939

Location of Khalkhyn Gol

Location of Khalkhyn Gol on the Asian mainland

Khalkhyn Gol Soviet offensive, 1939Japanese-captured Soviet equipment, Khalkhyn Gol, 1939

Left: The four-month conflict was named after the Khalkha River (Khal­khyn Gol), which flows through the battle­field. In Japan the conflict is known as the “Nomon­han Inci­dent,” named after a near­by vil­lage on the bor­der between Mon­go­lia (some­times infor­mally called Outer Mongolia) and Japanese-occupied Manchuria (Manchukuo).

Right: Japanese soldiers pose with captured Soviet equip­ment during one of the Battles of Khal­khyn Gol. After Japan’s occu­pa­tion of Korea (1905) and Man­chu­ria (1931), its mili­tary leaders in China, essen­tially army leaders, focused expan­sionist aims on Soviet Mon­go­lia and Siberia, and con­flicts occurred fre­quently on the Man­chu­rian bor­der from mid-1929 on­ward. The army’s aggres­sive plans on the Asian main­land some­times caught the civil­ian govern­ment in Tokyo by sur­prise, as the 1931 “Muk­den Inci­dent” (also known as the “Manchurian Incident”) in Northern China showed.

Mongolian soldiers, Khalkhyn Gol, 1939Mongolian cavalry, Khalkhyn Gol, 1939

Left: Soldiers of the Mongolian People’s Army fight against Japa­nese sol­diers, Khal­khyn Gol, 1939. The Mon­go­lian Peo­ple’s Repub­lic was pro­claimed in Novem­ber 1924 after Soviet troops expelled White Russian and Chinese forces from Mon­go­lia. Mon­go­lia then became a de facto puppet state of the Soviet Union.

Right: Mongolian cavalry during the Battle of Khal­khyn Gol, 1939. After Soviet and Mon­go­lian armed forces had defeated Japa­nese forces in the sum­mer of 1939, the warring parties entered into a truce, set up a com­mis­sion to define the Mon­go­lian-Man­chu­rian border later in the year, and entered into a neutrality pact that lasted until August 1945.

CapturedCaptured Japanese soldiers, Khalkhyn Gol, August 1939

Left: A Japanese light tank (Type 95 Ha-Go) captured by Soviet troops after the Battle of Khal­khyn Gol. Six years later, on August 9, 1945, Soviet forces in­vaded Man­chu­ria (Man­chu­kuo). The rapid defeat of Japan’s Kwan­tung Army, as its largest, most prestigious army on the Chin­ese main­land was called, was a signif­i­cant factor in Japan’s sur­render. Japa­nese leaders imag­ined the Red Army in Man­chu­ria as poised to in­vade the Home Islands with boots on the ground, while the Amer­i­cans were viewed as perfectly content to continue incinerating Japan from the skies.

Right: Captured Japanese soldiers, Khal­khyn Gol, August 1939. Khal­khyn Gol resulted in total defeat for the Japa­nese Sixth Army, a gar­ri­son force based in Manchukuo under the overall command of the Kwantung Army.

Khalkhyn Gol: History’s Forgotten Battle