After the An-Shi Rebellion was quelled, the remnants of An-Shi established the Feiyi Gang, which secretly roamed among the vassal states, formed alliances, and attempted to incite the generals to rise up in Hebei and profit from it. In order to eliminate the Feiyi thieves, the court ordered the swordsman Pei Mingong to recruit some swordsmen from the rivers and lakes to establish the Changshuimen. In the 12th year of Zhenyuan, the Feiyi Gang and the Changshuimen each set up many puzzles in Wei Bo, and the two sides launched a thrilling life-and-death battle here.