On August 11 the 386th was re-subordinated to the 88th Rifle Corps, still in 25th Army. On the previous two days advance units of the 108th and 113th Fortified Regions had captured Japanese positions across the Hunchun and Tumen rivers, north of the old 1938 battlefield at Lake Khasan. 88th Corps was committed to support the fortified regions and advanced on the Hunchun - Tumen axis. By August 14 Hunchun was taken by 113th Fortified Region, but as it advanced toward the Inanho River it faced heavy opposition from the Japanese 112th Infantry Division. The next day the 386th, supported by the 209th Tank Brigade, drove across the Inanho but ran into one regiment of the Japanese division, strongly entrenched, and several attempts to dislodge them failed. Late in the day the 258th Rifle Division from Corps second echelon crossed the Tumen at Hunyong to attack the Japanese right flank. On August 16 elements of the 113th Fortified Region extended their operations eastward on the division's right flank but ran into the remainder of the Japanese 112th, which held its positions, but by now was encircled on three sides by 25th Army. On the 17th the ring closed around the 112th and its neighboring 79th Infantry Division as 39th Corps secured Tumen while 88th Corps pushed aside a regiment of the 79th Infantry at Mayusan and occupied Onsang, ten km east of Tumen. Remaining Japanese units surrendered or fled into the hills south of the Tumen River.