Some people say that Sun Chengzong's defense line in Ning Guan, like Fan Zhongyan's fortress, is used for attack, not for defense. In fact, attack and defense are inseparable from "money"! What was lacking in the Ming Dynasty was money. If in the apocalypse, Sun Chengzong's fortress promotion plan can be said to be very suitable, but in the Chongzhen period, there was no money to pacify Liao! The financial problem of Ning Guan's defense line has always been a thorny issue, which makes Chongzhen a headache! This is why Chongzhen has been thinking about Liao Ping. Chongzhen can't always be a dead mouse. Because at that time, he had to spend not only on military affairs, but also on artillery and scientific research in Dengzhou and Laizhou, and even on Li Zicheng and Zhang!
What finally made Ning Guan a chicken rib was "Wuqiao mutiny"! Through the Wuqiao mutiny, the late Jin dynasty had firearms, which made the Ming dynasty take a big step of internal friction. Under the action of this kind of firearms, Ning Guan's defense has been advanced, and even defense has become a big problem! But Daming is dead. Why can't the Qing army enter the pass? This is also the importance of Ning Guan's defense. Quite simply, Ning Guan's defense line was vital to the stability of the Ming Dynasty. For the Ming dynasty, it was really a chicken rib and gave up. Huang taiji and dourgen will be eyeing the capital. If you don't give up, financial exports will be as unbearable as parasites!
In fact, the failure of Denglai and Dongjiang lies in Yuan Chonghuan killing Mao, Kong Youde Wuqiao mutiny, and then Dongjiang insurrection! There is nothing wrong with Ning Guan's defense! It can be said that Denglai and Dongjiang failed!