Khalkin Gol, Battle of

Crushing Soviet victory in August 1939 over the Japanese Kwangtung army on the border of Manchuria and Outer Mongolia, about 645 km/400 mi northwest of Harbin. It was the most disastrous defeat ever suffered by the Japanese army, but is largely unknown in the West because attention was focused on Poland at the time.

Japanese provocation The border between Mongolia and China generally follows the Khalkin River, but at this point cuts across a bend in the river, on the Manchurian side, for about 64 km/40 mi. In May 1939 the Japanese Kwangtung Army were probing the Mongolian border to find out just how serious the USSR was about the Pact of Mutual Assistance it had recently signed with Outer Mongolia. The Japanese therefore pushed beyond the border line to occupy the salient and relocate the border on the river. A combined force of cavalry and infantry crossed the line 11 May; the Mongolian border guards called for help and a squadron of Mongolian cavalry drove the invaders back.

Troop build-up Three days later the Japanese reappeared in greater strength, supported by aircraft and occupied the disputed area. A Soviet infantry unit some kilometres behind came up to the river, and over the next month each side fed more troops into the area and the line of contact moved to and fro over the disputed ground. By early July, the Japanese had 40,000 troops, 135 tanks, and 235 aircraft engaged. The Soviets now appointed General (later Marshal) Georgi Zhukov to settle the matter, giving him 12,500 troops, 135 tanks, and 225 aircraft. He confined his efforts to merely repulsing the Japanese whenever they moved, but this spurred them to greater effort and they increased their forces to 80,000 troops, with tanks, armoured cars, and artillery, and 450 aircraft. Zhukov had 35 infantry divisions, 20 cavalry squadrons, 500 guns, 500 tanks, and 600 aircraft in the area by August 1939.

Soviet attack On 20 August he launched an encircling attack, opening with an intense air strike followed by a two-hour artillery bombardment. By 31 August the entire Japanese 6th Field Army was surrounded and virtually destroyed, over 50,000 being killed or captured.