Japanese troops launched an assault on Soviet-held high ground near Lake Khasan, a remote corner where the borders of Manchukuo, Korea, and the USSR met. The eleven-day clash, fought with artillery and tanks over marshy terrain, ended in a costly Soviet victory that foreshadowed the larger defeat Japan would suffer a year later at Khalkhin Gol.
The fighting at Lake Khasan grew out of a territorial dispute so obscure that few outside the region could have located it on a map, yet it revealed the brittle state of Japanese-Soviet relations in the years before the Second World War. Japanese commanders in the Kwantung Army, emboldened by earlier successes in Manchuria, believed the Soviet Far East was vulnerable and probed its defenses.
Soviet Marshal Vasily Blyukher organized a counteroffensive that, despite early stumbles and heavy casualties on both sides, drove the Japanese back across the border by mid-August. Stalin, dissatisfied with the operation's costs, later had Blyukher arrested and executed in the purges.
The battle mattered less for its scale than for what it taught both militaries. Japan's General Staff underestimated Soviet mechanized power, a miscalculation repeated disastrously the following summer at Khalkhin Gol, while Moscow used the lessons to refine the armored doctrine Georgy Zhukov would later deploy against Germany.
Key people: Vasily Blyukher, Georgy Zhukov