In the first year of Duanping, the Battle of Caizhou wiped out the Jin Dynasty and avenged the humiliation, but the monarchs and ministers of the Southern Song Dynasty were faced with a choice - should they rush forward to regain the empty cities in the Central Plains, or stick to the river defense lines of Jingxiang, Huaihe, and Sichuan? The famous general Meng Gong fought against all opinions and brought the refugees from the Central Plains back south. With the four pillars of "clearing the country with strong walls, locking the rivers with naval forces, calming the people with garrison, and strengthening the army with firearms", he joined forces with Zhao Fan, Yu Jie, and Lu Wende. The other generals built a land and water defense line in Jingxiang, built water network barriers in Huaihe and Huaihe, and built mountain fortresses in Sichuan and Sichuan. They pushed the Southern Song Dynasty from "being peaceful and peaceful" to a strategic transformation of "defense as offense". When the Mongolian Great Khan Wokuotai's 100,000 cavalry marched south, Meng Gong led the navy and firearms troops to engage in a life-or-death duel with the Mongolian cavalry on the Han River and the Huaihe River. Using rivers as shields and gunpowder as blades, he composed an epic defense battle of the Southern Song Dynasty in which "the boat master defeated the cavalry."
