During the early weeks of the Sino-Japanese war, the IJA moved into Mongolia in order to cut supply routes from Soviet Russia. After romping through weak Chinese resistance, Lt. Gen. Itagakiís 5th Division turned to cross back over the Great Wall into northern China where growing Red Chinese guerilla activity had become a problem. Red Chinese general Lin Paio, ordered to take advantage of good intelligence, sent fast moving detachments to harass the enemy from the rear and to interdict their advance, while deploying his 115th Division in ambush along the mountain road between Pinghsing Pass and Laoyemaio.
Attacker: Red Chinese (Elements 115th Division)
Defender: Japanese (Elements 21st Infantry Brigade, 5th Infantry Division)