On May 11, 1939, a few hundred horsemen from Inner Mongolia (or occupied Manchuria), accompanied by their Japanese "advisers" from the 23rd Komatsubara Division, crossed the border and galloped to the village of Nomonhan. The inhabitants did not even have time to alert the border guards stationed in a log fort eight kilometers away, on the west bank. The next day, the invaders crossed the border again after an action closer to the traditional tribal conflict than the confrontation between two superpowers of the 20th century! A horde of screeching tsirik horsemen wheeled at full gallop around their hereditary enemies, the Bargut, led by the Japanese.
On May 14, the invaders returned in force, supported this time by 300 Japanese cavalry. It had only taken a few hours to lead the Tsirik back to the perimeter of the garrison. During the night, the local Soviet adviser, Major Bykov, was called in to help. The next morning, as he drove to this medieval site, the 20th century manifested itself in the form of a Japanese air raid that terrorized his men and left only ruins behind. As a precaution, Bykov requested the immediate dispatch of the 6th Mongolian Cavalry Division and the few detachments of Soviet troops available in the vicinity. But, while the reinforcements massed on the west bank of the river, the aggressors disappeared into thin air on the other bank.
On the night of May 22, Bykov cautiously carried out a reconnaissance in force across the river. The Japanese were waiting for him there, hidden in the tall grass of Nomonhan, and he had to fight furiously to get back to the Khalkhin-Gol.
The game of cat and mouse continued. On May 25, Bykov moved all his forces cautiously forward. The next two days were spent clearing the east bank and reoccupying the abandoned village of Nomonhan. On the Soviet side, there were now nearly 10,000 men engaged, mostly police forces, supported by a few specialized companies. The border incident was rapidly escalating, and on May 28 a new milestone was reached. Five thousand Japanese regulars, escorted by a tribal horde, fell before dawn on Bykov's troops. Only the caution with which this veteran of the Red Army had articulated his device allowed him once again to avoid being crushed and to regain the river. But the alarm signal had already been sounded in the Kremlin and, that same evening, the units of the Soviet 149th motorized infantry regiment gathered to immediately go into line. The battle continued throughout the night, and in the morning a Russo-Mongol counter-attack once again drove the Japanese back to the frontier. Their losses amounted to 400 men.