During the Second Sino- Japanese war 20,000 Japanese troops and 50 tanks invade Pa Tou Lou Tzu, or Badaling, a strategic point along the Great Wall of China. The defense of the Great Wall was one of the earliest battles, or "incidents," between Chinese and Japanese troops. The Chinese captured Japanese outpost after fierce battle. With stick grenades the Chinese disabled Japanese machine gun nests and killed all the Japanese inside. The Chinese outpost, with a force of seven men, held off the invading Japanese army for five days. First attack by Mongol mercenaries and Japanese troops failed and all Mongols were killed by the Chinese. On the sixth day, all 7 soldiers were killed in action. However, the outpost successfully covered for other Chinese forces to retreat. The seven soldiers tricked the Japanese army into believing there were a thousand Chinese troops defending the outpost.