Soviet–Japanese border conflicts
The Soviet–Japanese border conflicts were a series of minor and major conflicts fought between the Soviet Union, Mongolia and Japan in Northeast Asia from 1932 to 1939.
The Japanese expansion in Northeast China created a common border between Japanese-occupied Manchuria and the Soviet Far East. This led to growing tensions with the Soviet Union, with both sides often engaging in border violations and accusing the other of doing so. The Soviets and Japanese, including their respective client states of Mongolia and Manchukuo, fought in a series of escalating small border skirmishes and punitive expeditions from 1935 until Soviet-Mongolian victory over the Japanese in the 1939 Battles of Khalkhin Gol, which resolved the dispute and returned the borders to status quo ante bellum.
The Soviet–Japanese border conflicts heavily contributed to the signing of the Soviet–Japanese Neutrality Pact in 1941.
Prelude from 1904–1932
In the aftermath of the First Sino-Japanese War and the Eight Power Intervention against the Boxer Rebellion in China, the Qing hold over Manchuria and Korea had weakened significantly, leading to both the Russian and Japanese Empires vying for control over the territories.The Russo-Japanese War of 1904 to 1905 began when the Empire of Japan launched a surprise attack on the Russian Pacific Fleet stationed at Port Arthur on the Liaodong Peninsula. Following one and a half years of fighting between the Russian Army and the Japanese Army and the disastrous battle of Tsushima, the Russian Empire sued for peace, thereby recognizing Japan's claims to Korea and agreeing to evacuate Manchuria. Following the 1918 Siberian intervention by Japan in the Russian Civil War in the Russian Far East and fighting against Vladimir Lenin and the Soviet Bolshevik Communists from 1918 to 1922 after the Japanese took the German Qingdao Colony and the German Marshall Island Colonies from the German Empire in 1914 during WW1.
From 1918 to 1920 the Imperial Japanese Army were helping the White Army and Alexander Kerensky against the Bolshevik Red Army. In the same years they also helped the Czechoslovak Legion in Siberia to get back to Europe via the Trans-Siberian Railway. When the Czechoslovak Legion got back to Europe in 1920, Austria-Hungary had already collapsed and Czechoslovakia had been created two years before. Japan withdrew from the Russian Revolution and the Civil War in 1922. However, following its previous occupation in 1919 and the Soviet intervention in Mongolia of 1921, the Republic of China had to withdraw from Outer Mongolia in 1921. In 1922, after they captured Vladivostok in 1918 to stop the Bolsheviks in the Russian Far East during the Civil War, the Japanese had to retreat and withdraw back to Japan because the Bolsheviks led by Lenin were too powerful and everyone was tired of war after The Great War ended in 1918.
Following Hirohito's Japanese invasion of Manchuria in 1931–1932, violations of the borders between Manchukuo, the Mongolian People's Republic and the Soviet Union took place frequently. Many of them were misunderstandings due to insufficiently marked nature of the border, but some were intentional acts of espionage. Between 1932 and 1934, according to the Imperial Japanese Army, 152 border disputes occurred, largely because the Soviets infiltrated Manchuria for intelligence purposes. The Soviets blamed the Japanese for 15 cases of border violation, 6 air intrusions, and 20 episodes of "spy smuggling" in 1933 alone. Hundreds of other violations were reported by both sides throughout the following years. To make matters worse, Soviet-Japanese diplomacy and trust had declined even further, with the Japanese being openly called "fascist enemies" at the Seventh Comintern Congress in July 1935.
Minor clashes between the Soviets and Japanese
1935 Incidents
In early 1935 around January or February, the first shooting affray took place. From then until April 1939, the Imperial Japanese Army recorded 108 such incidents. On 8 January 1935, the first armed clash, the Halhamiao incident, occurred on the border between Mongolia and Manchukuo. Several dozen cavalrymen of the Mongolian People's Army trespassed in Manchuria near some disputed fishing grounds, and engaged an 11-man Manchukuo Imperial Army patrol unit near the Buddhist temple at Halhamiao, which was led by a Japanese military advisor. The Manchukuo Army incurred slight casualties, suffering 6 wounded and 2 dead, including the Japanese officer. The Mongols suffered no casualties, and withdrew when the Japanese sent a punitive expedition to reclaim the disputed area. Two motorized cavalry companies, a machine gun company, and a tankette platoon were sent and occupied the point for three weeks without resistance.In June 1935, the Japanese and Soviets directly exchanged fire for the first time when an 11-man Japanese patrol west of Lake Khanka was attacked by 6 Soviet horsemen, supposedly inside Manchukuo territory. In the ensuing firefight, one Soviet soldier was killed, and two horses were captured. While the Japanese asked the Soviets for a joint investigation of the issue, the Soviets rejected the request.
In October 1935, nine Japanese and 32 Manchukuoan border guards were engaged in setting up a post, about 20 kilometers north of Suifenho, when they were attacked by a force of 50 Soviet soldiers. The Soviets opened fire on them with rifles and 5 heavy machine guns. In the ensuing clash, two Japanese and four Manchukuoan soldiers were killed, and another 5 were wounded. The Manchukuoan foreign affairs representative lodged a verbal protest with the Soviet consul at Suifenho. The Imperial Japanese Army's Kwantung Army also sent an intelligence officer to investigate the scene of the clash.
On 19 December 1935, a Manchukuoan army unit engaging in a reconnoitering project southwest of Buir Lake clashed with a Mongolian party, reportedly capturing 10 soldiers. Five days later, 60 truck-borne Mongolian troops assaulted the Manchukuoans and were repulsed, at the cost of 3 Manchukuoan dead. The same day, at Brunders, Mongolian soldiers attempted to drive out Manchukuoan forces three times in the day, and then again at a night, but all attempts failed. More small attempts to dislodge the Manchukuoans from their outposts occurred in January, with the Mongolians this time utilizing airplanes for recon duty. Due to the arrival of a small force of Japanese troops in three trucks, these attempts also failed with a few casualties on both sides. Aside from the 10 prisoners taken, Mongolian casualties during these clashes are unknown.
1936 border incidents
In February 1936, Lieutenant-Colonel Sugimoto Yasuo was ordered to form a detachment from the 14th Cavalry Regiment and, in the words of Lieutenant-General Kasai Heijuro, "out the Outer Mongol intruders from the Olankhuduk region". Sugimoto's detachment included cavalry guns, heavy machine guns, and tankettes. Arrayed against him were 140 Mongolians, equipped with heavy machine guns and light artillery. On February 12, Sugimoto's men successfully drove the Mongolians south, at the cost of eight men killed, four men wounded, and one tankette destroyed. After this, they began to withdraw, but were attacked by 5-6 Mongolian armored cars and 2 bombers, which briefly wreaked havoc on a Japanese column. This was rectified when the unit obtained artillery support, enabling it to destroy or drive off the armored cars.In March 1936, the Tauran incident occurred. In this battle, both the Japanese Army and Mongolian Army used a small number of armored fighting vehicles and military aircraft. The Tauran incident of March 1936 occurred as the result of 100 Mongolian and six Soviet troops attacking and occupying the disputed village of Tauran, Mongolia, driving off the small Manchurian garrison in the process. They were supported by a handful of light bombers and armored cars, though their bombing sorties failed to inflict any damage on the Japanese, and three of them were shot down by Japanese heavy machine guns. Local Japanese forces counter-attacked, running dozens of bombing sorties on the village, and eventually assaulting it with 400 men and 10 tankettes. The result was a Mongolian rout, with 56 soldiers being killed, including three Soviet advisors, and an unknown number being wounded. Japanese losses amounted to 27 killed and nine wounded.
Later in March 1936, there was another border clash, this time between the Japanese and the Soviets. Reports of border violations led the Japanese Korean Army to send ten men by truck to investigate, but this party itself was ambushed by 20 Soviet NKVD soldiers deployed at a point 300 meters inside the territory claimed by the Japanese. After incurring several casualties, the Japanese patrol withdrew, and brought up 100 men within hours as reinforcements, who then drove off the Soviets. However, fighting erupted later in the day when the NKVD also brought reinforcements. By nightfall, the fighting had stopped and both sides had pulled back. The Soviets agreed to return the bodies of two Japanese soldiers who died in the fighting, which was seen as encouraging by the Japanese government.
In early April 1936, three Japanese soldiers were killed near Suifenho, in one of many minor and barely documented affrays. However, this incident was notable in that the Soviets again returned the bodies of the dead servicemen.