In the year 537, Eastern Wei send an advance guard of three army columns through the Tong Pass to attack Western Wei. The Western army under Yu-Wen Tai defeat one of the columns while the others retreat. Yu-Wen follows up, but runs into the main Eastern army (200,000 men). The Westerners are push back through the pass and the Eastern army emerge from the mountains. Unexpectedly they are charged in the flank by 10,000 Western cavalry, and 6,000 Easterners are killed and 70,000 captured.