In the second year of Duanping in the Southern Song Dynasty (1235), Mongolian Khan Wokuotai invaded the Song Dynasty on a large scale, and Sichuan, Sichuan and Song Jun were always at a disadvantage. The Mongols invaded Sichuan several times, each time burning, killing and looting, and retreating northward with their belongings, as if entering and leaving no man's land. The whole of Sichuan is ravaged by Mongolian army almost all the time, which has caused serious damage to social economy. In the first year of Chunyou (124 1), Wokuotai died of illness, and there was a dispute over the inheritance right of Khan in Mongolia, and the Mongolian-Song War came to an end temporarily.

In the second year of Chunyou (1242), Li Zong ordered Yu Jiechu, a famous strategist in the Southern Song Dynasty, to take full charge of Sichuan's military and political affairs. Yujie generously promised to return the whole province to the court within ten years. During his tenure, he changed his bad politics, plowed the fields and accumulated grain, and coached the army. In addition, a hall for recruiting talents was set up on the left side of Shuaifu yamen, and the slogan of "gathering people to think and benefiting loyalty" was put forward. In particular, it adopted the suggestion of Ranjin and Ranpu brothers "choosing risks, appointing people, accumulating millet, stationing troops and moving cities", and moved Hezhou (now Hechuan, Sichuan) to Yushan to build a city and build a base, making it a military center; Later, more than ten sturdy mountain cities were built as military fortresses, and counties were moved to mountain cities to save money, food and property to prevent the invasion of Mongolian troops.

In the eleventh year of Chunyou (125 1), Mongolian kings pushed Dai Mengge as a great Khan. With the unification of power, Mongolia began to actively implement the strategy of destroying the Southern Song Dynasty. The following year, the Mongolian army entered Tubo, and then attacked Dali. In less than two years, the siege of the Southern Song Dynasty was completed. At this time, listening to rumors, he destroyed the Great Wall, dismissed Yu Jie, who actively defended Shu, and called him back to the DPRK. Yu Jie was forced to commit suicide by taking poison. At this time, the Southern Song Dynasty will face a severe moment when the Mongolian army launched a larger invasion.