Battle of Lake Khasan

The Battle of Lake Khasan (July 29, 1938 – August 11, 1938) and also known as the Changkufeng Incident (Russian: Хасанские бои, Chinese and Japanese: 張鼓峰事件; Chinese Pinyin: Zhānggǔfēng Shìjiàn; Japanese Romaji: Chōkohō Jiken) in China and Japan, was an attempted military incursion of Manchukuo (Japanese) into the territory claimed by the Soviet Union. This incursion was founded in the beliefs of the Japanese side that the Soviet Union misinterpreted the demarcation of the boundary based on the Treaty of Peking between Imperial Russia and the Manchu Empire (and subsequent supplementary agreements on demarcation), and furthermore, that the demarcation markers were tampered with.

Background
For most of the first half of the twentieth century there was considerable tension between Moscow, Tokyo and Beijing along their common borders in what is now North East China. The Chinese Eastern Railway or (CER) was a railway in northeastern China (Manchuria). It connected China and the Russian Far East. The southern branch of the CER, known in the West as the South Manchuria Railway, became the locus and partial casus belli for the Russo-Japanese War and subsequent incidents leading to the Second Sino-Japanese War, and a series of Soviet-Japanese Border Wars. Larger incidents included the Sino-Soviet conflict of 1929 and the Mukden Incident between Japan and China in 1931. The battle of Lake Khasan was fought between two powers which had long distrusted each other.

The confrontation was triggered when the Soviet Far East Army and Soviet State Security (NKVD) Border Guard reinforced its Khasan border with Manchuria. This was prompted in part by the famous defection one month before of Soviet General G.S. Lyushkov, in charge of all NKVD forces in the Soviet Far East at Hunchun, located in the heart of the Tumen River Area. He provided the Japanese with critical intelligence on the poor state of Soviet Far Eastern forces and the wholesale purge of army officers

Events
On July 6, 1938 the Japanese Kwantung Army intercepted and decoded a message sent by the Russian commander in the Posyet region to Soviet headquarters in Khabarovsk. The message recommended that Russian soldiers be allowed to secure previously unoccupied high ground west of Lake Khasan, most notably the disputed Changkufeng Heights, because it would be advantageous for the Soviets to occupy terrain which overlooked the Korean port-city of Rajin, as well as strategic railways linking Korea to Manchuria. Within the next two weeks, small groups of Soviet border troops then moved into the area and began fortifying the mountain, constructing emplacements, observation trenches, entanglements, and communications facilities.

At first, the Japanese Korean Army, which had been assigned to defend the area, disregarded the Soviet advance. However, the Kwantung Army, whose administrative jurisdiction overlapped Changkufeng, pushed the Korean Army to take more action because it was suspicious of Soviet intentions. Following this, the Korean Army took the matter to Tokyo, recommending that a formal protest be sent to the USSR.

The conflict started on July 15, when the Japanese attaché in Moscow demanded the removal of Soviet border troops from the Bezymyannaya (сопка Безымянная, Chinese name: Shachaofeng) and Zaozyornaya (сопка Заозёрная, Chinese name: Changkufeng) Hills to the west of Lake Khasan in the south of Primorye, not far from Vladivostok, claiming this territory by the Soviet–Korea border. The demand was rejected.

The first Japanese attack on July 29 was repelled, but on July 31 the Soviet troops had to retreat. The Japanese 19th Division along with some Manchukuo units took on the Soviet 39th Rifle Corps under Grigori Shtern (eventually consisting of the 32nd, 39th, and 40th Rifle Divisions, as well as the 2nd Mechanised Brigade). One of the Japanese Army Commanders at the battle was Colonel Kotoku Sato, the commander of the 75th Infantry Regiment. Sato's forces expelled Russian troops from the hill in a night sortie, the execution of which became a Japanese model for assaults on fortified positions.

It was also reported that during the Changkufeng Incident the Japanese orchestrated frontal assaults with light and medium tanks which were immediately followed by Russian tank and artillery counter-attacks. In 1933, the Japanese designed and built a "Rinji Soko Ressha" (Special Armored Train). The train was deployed at "2nd Armored Train Unit" in Manchuria and participated in the Second Sino-Japanese War and the Changkufeng conflict against the Soviets transporting thousands of Japanese troops to and from the battlefield, displaying to the West the ability of an Asian nation capable of adopting and implementing Western ideas and doctrine concerning rapid infantry deployment and transportation.

On 31 July, People's Comissar for Defense Kliment Voroshilov ordered combat readiness for 1st Coastal Army; Pacific Fleet was mobilized as well.

Under the command of the chief of the Far East Front, Vasily Blücher, additional forces were moved to the zone of conflict and after several engagements during August 2–9 the Japanese forces were disastrously defeated and thrown out of the Soviet territory.

On August 10, the Japanese prime minister sent to the United States asked for peace and the hostilities ceased on August 11.

Consequences
The Japanese military, while seriously analyzing the results of the battle, would later engage with the Soviets once more, with disastrous results, in the more extensive Battle of Khalkhin Gol (Nomonhan) in the Soviet-Japanese Border War of 1939. This second engagement resulted in the defeat of the Japanese Sixth Army.

The Soviet losses were blamed on the incompetence of Vasily Blücher. On October 22 he was arrested by the NKVD and later thought to have been tortured to death.

26 Soviet officers and soldiers for their participation in the battle were awarded the title Hero of the Soviet Union, 95 were awarded the Order of Lenin