Japan ruled part of Inner Mongolia when it ruled Manchuria in northern China in from 1931 to 1945 and planed to create a Japanese puppet state in Mongolia. In the 1930s the Japanese formed a new government (Meng-Jiang) in central Inner Mongolia headed by Mongolian prince Demchigdonggrud (Dewang).

From the mid-1930s until the end of World War II, some parts of what is now Inner Mongolia was occupied by the Japanese and others by the Chinese Communists. In 1936 Mao Zedong told Edgar Snow, "As for Inner Mongolia, which is populated by both Chinese and Mongolians, we will struggle to drive Japan from there and help Inner Mongolia establish and autonomous state...when the people's revolution has been victorious in China, the Outer Mongolian Republic will automatically become part of the Chinese federation, at its own will.”

Mongolia's easternmost portion is a salient jutting deep into Manchuria. A branch railroad runs from Changchun on the Shenyang-Harbin railroad to within a few kilometers of the border; on the other side of the frontier, the Halhin Gol runs parallel to the border on the Mongolian side for about 70 kilometers. This area had been the scene of serious clashes in early 1935. To facilitate military deployment into this vulnerable area, the Soviet Union built a wide-gauge railroad, completed in 1939, connecting the Chinese-Eastern railroad to the Mongolian town of Choybalsan.

Japanese Threat on Mongolia

Japan's occupation and annexation of neighboring Manchuria in 1931 left no doubt of Tokyo's long-range objectives in Northeast Asia. A program of subversion among the Mongolians and of agitation in support of pan-Mongolism was followed by minor clashes along the Mongolian-Manchurian border in 1934 that reached major intensity in 1935. After serious clashes with the Japanese along the eastern Mongolian border in early 1935, a conference of Mongolian and Japanese representatives was convened in June at the Chinese border town of Manzhouli to settle border demarcation and other matters. After six months without reaching agreement, the effort was abandoned. [Source: Library of Congress, June 1989 *]

On March 1, 1936, Josef Stalin publicly and unequivocally stated that "If Japan should venture to attack the Mongolian People's Republic and encroach upon its independence, we will have to help the Mongolian People's Republic...just as we helped in 1921...." Two weeks later, a Protocol Treaty of Friendship and Mutual Assistance reiterated the main provisions of the 1934 agreement. Apparently the Soviets at the time were less concerned about Chinese sensibilities than they had been earlier. The protocol was to run for ten years; it provided for joint consultation and protective action in the event of threat to either party by a third power, for military assistance in the case of a third-power attack, and for the stationing of troops in each other's territory as necessary. Some Soviet troops had remained in Mongolia after the suppression of the revolts; when Japan invaded northern China and occupied Inner Mongolia, this treaty provided a basis for increasing Soviet strength to a reinforced corps, the Fifty- seventh Independent Rifle Corps. *

In 1937 the Japanese invaded northern China, which enabled Japanese forces to occupy the Inner Mongolian provinces of Qahar and Suiyuan along Mongolia's southern border. This widened the zone of contact between Mongolian and Japanese forces and increased Mongolian security problems. Incidents continued along the Mongolian borders with Manchuria and Inner Mongolia. In July 1938, the Japanese Guandong (Kwantung in Wade-Giles romanization) Army (the Japanese army in Manchuria, 1931-45) mounted a major, yet unsuccessful, attack against Soviet positions in an ambiguously demarcated area along the Manchurian-Siberian border near Vladivostok. Frustrated along the Siberian border, Japan turned the following year to the more vulnerable Mongolian border, where it thought that subversion against the Mongolians would pave the way. *

Mongolia in World War II

Stalin took the Japanese threat very seriously and strengthened the Mongolian armed forces and ultimately conscripted 10 percent of Mongolia’s population into the military. When Japan invaded Outer Mongolia in 1939, the Japanese were soundly defeated by a joint Mongolian-Soviet force. Largely as a result of this face off, Japan signed a neutrality pact with Soviet Union.

Soviet General Georgi Zhukov commanded the Soviet-Mongolian army that met this invasion. Between May and September 1939, there was large-scale ground and aerial fighting along the Khalkhyn Gol, a river in northeastern Mongolia. The Mongolian troops and their Soviet allies severely defeated the Japanese, who may have sustained as many as 80,000 casualties compared with 11,130 on the MongolianSoviet side. Hostilities ended on September 16, 1939. The Soviet Union and Japan signed a truce, and a commission was set up to define the Mongolian-Manchurian border. Although Japan did not invade again, it did mass large military forces along the Mongolian and the Soviet borders in the course of the war, while continuing its southward drive into China. [Source: Library of Congress, June 1989 *]

Japanese Invasion of Mongolia

The frequency of border clashes increased until they occurred almost daily in this area during 1938 and early 1939. In early May 1939, Soviet foreign minister Vyacheslav M. Molotov issued another stern warning to Japan: "I give warning that the borders of the Mongolian People's Republic will be defended by the USSR as vigorously as we shall defend our own borders." [Source: Library of Congress, June 1989 *]

On May 11, 1939, the Japanese army occupied portions of Mongolia between the border and the Halhin Gol. A combined Mongolian-Soviet force quickly moved against the invaders. By the end of May, the joint force had seized a bridgehead on the Halhin Gol's eastern bank. To counter this move, the Japanese by early July concentrated a corps of 38,000 troops and attacked the northern flank of the Mongolian-Soviet bridgehead. The Japanese drove the allies back across the Halhin Gol, crossed it themselves, and established their own bridgehead on the western bank. On July 5, 1939, Soviet armor counterattacked and eliminated the Japanese bridgehead, after which both sides began a major force buildup. *

During July 1939, the Mongolian-Soviet forces were reorganized. The Trans-Baykal Military District was set up as a front headquarters, with the First Army Group under General Georgi Zhukov as the striking force. Soviet forces were concentrated in eastern Mongolia, and the Mongolian army mobilized to its full strength of 80,000 in eight cavalry divisions; the 515 aircraft of the combined force were used mostly in screening the southern borders. Zhukov's First Army Group included Mongolia's Sixth and Eighth Mongolian cavalry divisions, both of which were employed as flank protection for the army group along the 70-kilometer front on the Halhin Gol. During July and early August, the Japanese forces, setting August 20, 1939, as the target date, prepared to cross the river and to destroy the opposing forces. *

Soviet-Mongolian Defeat Japanese

The Japanese decision to attack must have been based on faulty intelligence or on extreme overconfidence, because the Japanese were weaker in infantry battalions by 30 percent, in tanks by 60 percent, and in aircraft by 25 percent. Further, Soviet intelligence was superior to the Japanese, because the Soviets had detected the Japanese buildup for the attack and had evidently correctly estimated its timing. At dawn August 20, 1939, the commander of the Mongolian-Soviet troops preempted the Japanese attack: 150 bombers struck Japanese positions, rear areas, and lines of communication. A ground attack by the southern and the northern wings of the First Army Group penetrated the Japanese flank with armor and infantry, and then they turned inward in a classic double envelopment as Mongolian cavalry protected the outer flanks. [Source: Library of Congress, June 1989 *]

The Japanese defended tenaciously, but by August 23 the Soviets had encircled the Japanese forces along the Halhin Gol. For five days, the Mongolian-Soviet forces beat back fierce attacks by Japanese relief forces as well as attempts by the surrounded units to break out. Japanese relief attempts slackened, and pockets of resistance were cleared out. On August 31, 1939, the Mongolian-Soviet forces advanced to the frontier. The Japanese conceded defeat and a cease-fire took effect on September 16, 1939. *

Soviet casualties came to nearly 10,000, and the Mongolians lost 1,130. Japanese losses were far greater, with more than 18,000 killed and 25,000 wounded (some total estimates were as high as 80,000). More than 170 guns and 200 aircraft were lost. After the defeat, Japan turned its military thrust southward. On June 9, 1940, an agreement fixing the Manchukuo-Mongolian border was signed in Moscow. This was followed on April 13, 1941, by the Soviet-Japanese Neutrality Pact, which included a Soviet pledge to recognize the territorial integrity of Manchukuo and a similar Japanese pledge with respect to Mongolia. Germany's invasion of the Soviet Union in June 1941 and the entry of the United States into World War II in December fully committed the Soviet Union and Japan to other flanks of their respective domains; thus, their Mongolian flanks remained relatively quiet until the final weeks of World War II. *

Mongolia as a Producer for the Soviet Union in World War II

Through most of World War II Mongolia produced agricultural and industrial development in support of Moscow's war efforts and made Mongolia a critical buffer in the Soviet Far Eastern defense system. Technically neutral, Mongolia declared war against Japan only in August 1945. The Soviet-Japanese Neutrality Pact, signed on April 13, 1941, obtained a commitment from Japan to respect Mongolia's territorial integrity. *

The Soviet position in Mongolia was now fully consolidated. Throughout World War II, Choybalsan followed Moscow's directives, and Mongolia supported the Soviet Union with livestock, raw materials, money, food, and military clothing. The Mongolian army was maintained intact throughout the war; it served as an important buffer force in the Soviet Far East defense system, but it did not actually join the Red Army. *

Mongolia stayed mobilized at the 80,000-troop level to guard its frontiers and to discourage any further Japanese incursion. Mongolia also devoted extensive resources to its part of the 1936 mutual-assistance pact, providing the Soviet armed forces with winter clothing, wool, hides, leather goods, meat, and almost half a million ponies and horses for draft and remount use from 1941 to 1945. The Mongolian people raised the money for a brigade of tanks, named the Revolutionary Mongolian Tank Brigade, and for a squadron of aircraft, named Mongolian Herdsmen, presented to the Red Army. In August 1945, Mongolian and Soviet forces joined in the invasion of Manchuria and Inner Mongolia, destroyed the greatly weakened Japanese army, and achieved Soviet political and military goals in northeastern Asia. *

Modernizing the army and keeping it at peak mobilization was a heavy drain on the nation's undeveloped economy and small population. Even so, the party leaders pressed on with what limited social progress they could manage in a wartime situation. As more teachers became trained, literacy began to accelerate, and government efforts to assist the herdsmen in sheltering, feeding, and caring for their livestock continued. Stock raising bore the major war burden, however, and with large Soviet requisitions to fill, herd totals fell sharply during the war. *

Mongolia at the End of World War II

Mongolians joined the Soviet campaign against Japan in the last two weeks of World War II. On August 10, 1945, two days after the Soviet Union had declared war on Japan, Mongolia also declared war on Japan. The Mongolian army, some 80,000 strong, joined Soviet troops in invading Inner Mongolia and Manchuria.

On August 14, 1945, in the Sino-Soviet Treaty of Friendship and Alliance, China agreed to recognize the independence of Mongolia within its "existing boundary," provided that a plebiscite confirmed the Mongolian people's desire for independence. Mongolia obliged, and in an October 20 referendum, 100 percent of the electorate voted for independence from China. On January 5, 1946, China recognized Mongolian independence and, on February 14, agreed to exchange diplomatic representatives. None, however, were exchanged. The ensuing Chinese civil war and the victory of the Chinese communists over the Guomindang government in 1949 led instead to Ulaanbaatar's recognition of the new People's Republic of China. [Source: Robert L. Worden, Library of Congress, June 1989 *]

After World War II, the Soviets detained 575,000 prisoners, including many Japanese rounded up in Manchuria. Around 14,000 of these were marched to Mongolia, where an estimated 2,000 died while doing forced labor. The Soviet Union absorbed the Tuvian republic in the northwest tip of Mongolia in 1944. *

Image Sources:

Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, Lonely Planet Guides, Library of Congress, U.S. government, Compton’s Encyclopedia, The Guardian, National Geographic, Smithsonian magazine, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Wall Street Journal, The Atlantic Monthly, The Economist, Foreign Policy, Wikipedia, BBC, CNN, and various books, websites and other publications.

Last updated April 2016

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