Moscow, Soviet Union August 20, 1939

The Soviet Union and Japan, two expansionist powers that occupied por­tions of the Asian main­land, had butted heads as early as 1904–1905 (the Russo-Japanese War) over influ­ence in China, Mongo­lia, and Man­churia, the latter country rich in coal, iron, and grains. In Septem­ber 1931 soldiers in the Kwan­tung Army, as Japan’s largest, most presti­gious army on the Chinese mainland was called, used a ruse—the so-called Mukden Inci­dent—to seize Man­churia, which bordered the Japanese colony of Korea on the east and, on the west, Mongo­lia, a de facto puppet state of the Soviet Union. The Kwan­tung Army named their Manchurian conquest Manchukuo and installed a puppet government there.

The Kwantung Army quickly embarked on a program of detaching pro­vinces on Man­chukuo’s border with China and turning them into buffer zones or client states. In July and August 1938 and again from May to August 1939, the Kwan­tung Army pro­voked two border wars, the Zhang­gufeng (Chang-ku-feng) Inci­dent and the Nomon­han (or Khal­khyn Gol) Incident, with the Soviet Union. Both con­flicts were stage-managed by local com­manders with­out the concur­rence of the War Ministry in Tokyo. In the first “incident” insub­or­di­nate units in the Kwan­tung Army and the Japa­nese Army in Korea launched an attack across the Soviet border on July 29, 1938, and chased the Soviets off Zhang­gufeng, a stra­tegic hill in the area where the south­eastern border of Man­chu­kuo inter­sected with the boun­daries of the Soviet Mari­time Pro­vince and Korea. Soviet infantry troops numbering 23,000, with tanks and armored vehicles and supported by heavy artillery and air cover, retook the hill on August 9 at a steep price. Two days later the countries entered into a truce.

The reality of Japan’s defeat made no impres­sion on local com­manders, for next spring they launched several more unsanc­tioned mili­tary actions against Soviet forces in the vicinity of Nomon­han, a village on the border between Man­chu­kuo and Mongolia (see map). On this date, August 20, 1939, days before the German inva­sion of Poland, the two adver­saries began a mas­sive ten-day tank battle near the Mongo­lian Khal­kha River that resulted in a spec­tac­ular Japanese defeat. It was the largest tank battle the world had yet seen and arguably the first decisive battle of the Second World War.

The Japanese defeat at Khal­khyn Gol 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 and east of Man­chu­kuo. 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, the Nether­lands, Britain, and France—all of which had resource-rich but ill-defended posses­sions there—as weaker opponents than the Soviets on the Asian mainland.

Japan’s strategic change in course, prompted by its second battlefield loss to the Soviets in as many years, even­tually led to a change in that country’s expan­sionist for­tunes, beginning with its success­ful attacks on the Philip­pines, the Dutch East Indies (Indo­nesia), British Malaya (Malay­sia), Singa­pore, and the Amer­i­can posses­sion of Hawaii on Decem­ber 7 and 8, 1941. Sadly for Japan, the change in course also presaged its tragic downfall.

Battles of Khalkhyn Gol: Japan versus the Soviet Union, May 11 to Septem­ber 15, 1939

Location of Khalkhyn Gol

Above: Location of Khalkhyn Gol on the Asian mainland. The Kwan­tung Army’s take­over of Man­churia in 1931 brought Japanese and Soviet armed forces toe to toe along a 3,000‑mile border. Numerous border skir­mishes and disputes punc­tuated the next several years as both sides rein­forced their respec­tive forces. In 1936 the Soviets signed a mutual assis­tance treaty with Mon­golia (some­times infor­mally called Outer Mon­golia), and in 1938 stationed forces in that country.

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

Left: A three-man Soviet BT-7 light cavalry tank on the offen­sive, Khalkhyn Gol, August 1939. 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 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 com­manders, focused expan­sionist aims on the Soviet Mari­time Pro­vince adja­cent to Korea’s north­east, Siberia, and Soviet Mon­go­lia, 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) and the 1938 Zhanggufeng (Chang-ku-feng) Incident 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 was a signif­i­cant factor in Japan’s sur­render to the Allies. 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 air.

Right: Captured Japanese soldiers, Khal­khyn Gol, August 1939. Khal­khyn Gol resulted in a total defeat for the Japa­nese Sixth Army, a gar­ri­son force based in Man­chu­kuo under the over­all command of the Kwan­tung Army. The 23rd Divi­sion, the primary Japa­nese infantry divi­sion involved in the Battle of Khal­khyn Gol, suffered 11,958 men killed, or about 80 per­cent of its combat strength, including most of its regimental commanders.

Khalkhyn Gol: History’s Forgotten Battle