Joke Collection Website - Talk about mood - Tell me why "Shi Qian burned Cuiyun Tower + Wu Yong outsmarted Daming Mansion" embodies the tactical strategy of "cooperating with the outside"?

Tell me why "Shi Qian burned Cuiyun Tower + Wu Yong outsmarted Daming Mansion" embodies the tactical strategy of "cooperating with the outside"?

Wu Yong wanted to ambush in the city of Beijing during the Lantern Festival, cooperate inside and outside, break the city and save people. Wu Yong also told Song Jiang that Cai Taishi in Tokyo was strongly advocating for peace. Lanterns are put off during the Lantern Festival in Beijing. Liangshanpo Songjiang defended the stronghold, and Wu Yong led eight groups of troops to garrison the city. Shi Qian set fire to Cuiyun Tower in Beijing, causing chaos in the city. Liang Zhongshu could not get out of the four city gates. Then he took the road away from the south gate. In the city, Chai Jin rescued Lu Junyi and Shi Xiu, and captured Li Gu and Jia.