Following Japan's full invasion of China in July 1937, the Soviet Union sent the 57th Special Corps led by Ivan Konev to Mongolia.

On 13 June, Genrikh Lyushkov, a Soviet NKVD major general who knew Stalin personally, defected to Japan for fear of the Great Purge.

The Japanese maintained that the border between Manchukuo and Mongolia was the Khalkhin Gol (English "Khalkha River") which flows into Lake Buir.

The Mongolian troops mainly consisted of cavalry brigades and light artillery units, and proved to be effective and agile, but lacked armor and manpower in sufficient numbers.

On 5 June, Zhukov, the new corps commander, arrived, and brought more motorized and armored forces (I Army Group) to the combat zone.

[34] Throughout June there were reports of Soviet and Mongolian activity on both sides of the river near Nomonhan and small-scale attacks on isolated Manchukoan units.

The order of battle was thus: The northern task force succeeded in crossing the Khalkhin Gol, driving the Soviets from Baintsagan Hill, and advancing south along the west bank.

Meanwhile, the 1st Tank Corps of the Yasuoka Detachment (the southern task force) attacked on the night of 2 July, moving in the darkness to avoid the Soviet artillery on the high ground of the river's west bank.

A pitched battle ensued in which the Yasuoka Detachment lost over half its armor, but still could not break through the Soviet forces on the east bank and reach the Kawatama Bridge.

[39] The two armies continued to spar with each other over the next two weeks along a four-kilometre (2.5 mi) front running along the east bank of the Khalkhin Gol to its junction with the Holsten River.

[41] On 23 July, the Japanese launched another large-scale assault, sending the 64th and 72nd Infantry Regiments against Soviet forces defending the Kawatama Bridge.

[54] By contrast, Tokyo's oft-stated desire that it would not escalate the fighting at Khalkhin Gol proved immensely relieving to the Soviets, freed to hand-pick select units from across the military to be concentrated for a local offensive without fear of Japanese retaliation elsewhere.

[34][60][61] Japanese military records reported approximately 20,000 battle and non-battle casualties, 162 aircraft lost in combat, and 42 tanks disabled (of which 29 were later repaired and redeployed).

[34] According to the Sixth Army's medical data, Japanese casualties amounted to 7,696 killed, 8,647 wounded, 1,021 missing, and 2,350 sick, for a total of 19,714 personnel losses.

Of the Soviet tank losses, 75–80% were destroyed by anti-tank guns, 15–20% by field artillery, 5–10% by infantry-thrown incendiary bombs, 2–3% by aircraft, and 2–3% by hand grenades and mines.

[70] The combatants remained at peace until August 1945, when the Soviet Union declared war on Japan and invaded Manchukuo and other territories after the atomic bombing of Hiroshima.

This defeat combined with the Chinese resistance in the Second Sino-Japanese War,[73] together with the signing of the Nazi-Soviet non-aggression pact (which deprived the Army of the basis of its war policy against the USSR), moved the Imperial General Staff in Tokyo away from the policy of the North Strike Group favored by the Army, which wanted to seize Siberia for its resources as far as Lake Baikal.

[74] Instead, support shifted to the South Strike Group, favored by the Navy, which wanted to seize the resources of Southeast Asia, especially the petroleum and mineral-rich Dutch East Indies.

[75] Because of this, Japan's focus was ultimately directed to the south, leading to its decision to launch the attack on Pearl Harbor on 7 December of that year.

Despite plans being made for a potential war against the USSR (particularly contingent on German advances towards Moscow), the Japanese never launched an offensive against the Soviet Union.

[78] In the closing months of World War II, the Soviet Union annulled the Neutrality Pact and invade the Japanese territories in Manchuria, northern Korea, and the southern part of Sakhalin island.

A year after defending Moscow against the advancing Germans, Zhukov planned and executed the Red Army's offensive, i.e. Operation Uranus, at the Battle of Stalingrad, using a technique very similar to Khalkhin Gol, in which the Soviet forces held the enemy fixed in the center, built up an undetected mass force in the immediate rear area, and launched a pincer attack on the wings to trap the German army.

Although their victory and the subsequent negotiation of the Soviet–Japanese Neutrality Pact secured the Far East for the duration of the Soviet-German War, the Red Army always remained cautious about the possibility of another, larger Japanese incursion as late as early 1944.

In December 1943, when the American military mission proposed a logistics base be set up east of Lake Baikal, the Red Army authorities, were according to Coox, "shocked by the idea and literally turned white".

For example, on 1 July 1942, Soviet forces in the Far East consisted of 1,446,012 troops, 11,759 artillery pieces, 2,589 tanks and self-propelled guns, and 3,178 combat aircraft.

IGHQ also dispatched General Tomoyuki Yamashita to Germany in order to learn more about tank tactics, following the crushingly one-sided Battle of France and the signing of the Tripartite Pact.

In spite of their recent experience and military improvements, the Japanese generally continued to underestimate their adversaries, emphasizing the courage and determination of the individual soldier as a way to make up for their lack of numbers and smaller industrial base.

To varying degrees, the basic problems that faced them at Khalkhin Gol would haunt them again when the Americans and British recovered from their defeats of late 1941 and early 1942 and turned to the conquest of the Japanese Empire.

The original Japanese doctrine explicitly forbade first aid to fellow soldiers without prior orders from an officer, and first-aid training was lacking.

To reduce susceptibility to diseases, future Japanese divisions commonly included specialized Epidemic Prevention and Water Purification Departments.