Relations between the USSR and Japan in 1938 cannot be called friendly even with the greatest stretch.
As a result of the intervention against China on a part of its territory, namely in Manchuria, the pseudo-state of Manzhou-Go, governed from Tokyo, was created. Since January 1938, Soviet military specialists took part in the fighting on the side of the Celestial Army. The latest equipment (tanks, planes, artillery air defense systems) was shipped to the ports of Hong Kong and Shanghai. It was not hiding.
By the time the conflict on Lake Hassan arose, Soviet pilots and Chinese colleagues trained by them had already destroyed dozens of Japanese aircraft in the air, launched a series of bombing strikes at airfields and military bases. They also sank the Yamato aircraft carrier in March.
A situation has ripened in which the Japanese leadership, striving for expansion of the empire, was interested in testing the strength of the ground forces of the USSR. The Soviet government, confident in its capabilities, behaved no less decisively.
The conflict at Lake Hassan has its own background. On June 13, the Manchu border was secretly crossed by Genrikh Samuilovich Lyushkov, the plenipotentiary representative of the NKVD, who oversaw intelligence work in the Far East. Turning to the side of the Japanese, he revealed to them many secrets. He had something to tell ...
The conflict on Lake Hassan began with a seemingly insignificant fact of reconnaissance of Japanese topographic divisions. Any officer knows that the compilation of detailed maps precedes the offensive operation, and this is what the special units of the probable enemy did in the two border hills Zaozernaya and Bezymyannaya, near which there is a lake. On July 12, a small detachment of Soviet border guards occupied the heights and dug in on them.
It is possible that these actions would not entail an armed conflict near Lake Hasan, but there is an assumption that it was the traitor Lyushkov who convinced the Japanese command of the weakness of the Soviet defense, otherwise it would be difficult to explain the further actions of the aggressors.
On July 15, a Soviet officer shoots the Japanese gendarme, who clearly provoked him to this act, and kills him. Then the border begins to break postmen with letters demanding to leave the skyscrapers. These actions did not succeed. Then, on July 20, 1938, the Japanese ambassador in Moscow presents the ultimatum to the People’s Commissar Litvinov, which produced about the same effect as the mentioned items.
On July 29, a conflict began on Lake Hassan. Japanese gendarmes went to storm the heights of Zaozernaya and Bezymyannaya. There were few of them, the whole company, but there were only eleven border guards, four of them died. A platoon of Soviet soldiers rushed to the rescue. The attack was repelled.
Further - more, the conflict at Lake Hassan gained momentum. The Japanese used artillery, then captured the hills by the forces of two regiments. An attempt to drive them out right away was unsuccessful. They demanded from Moscow to destroy the heights together with the troops of the aggressor.
Heavy TB-3 bombers were lifted into the air, they dropped more than 120 tons of bombs on enemy fortifications. Soviet troops had such a tangible technical advantage that the Japanese simply did not have any chance of success. The BT-5 and BT-7 tanks were not very effective on swampy soil, but the enemy did not have such.
On August 6, the conflict on Lake Hassan ended with the complete victory of the Red Army. Stalin drew from it the conclusion about the weak organizational qualities of the OKDVA commander V.K. Blucher. For the latter, it ended in failure.
The Japanese command did not make any conclusions, obviously believing that the reason for the defeat was only in the quantitative superiority of the Red Army. Ahead was Khalkhin Gol.