During the Chongzhen period, there were heavy clouds of war in Liaodong. As the son-in-law of Ningyuan Guardsman, Gu Yanzhou was full of arithmetic and strange ideas, but he was despised. He foresaw the unrivaled field advantage of the Houjin Iron Cavalry, and fought against all opinions to reshape Ningyuan city defense with the "bastion" concept. Relying on accurate terrain surveying and mapping, he constructed an exquisite "triangular defense system" and used parabolic equations to calculate the blind spots of artillery fire. In the shadow of the tragic defeat of Saerhu, the "Liaodong Eyeliner Network" was quietly woven, training soldiers in basic surveying and intelligence analysis, and predicting the movements of enemy chiefs from marching speed and supply patterns. Holding the "City Defense Deduction Sandbox" in hand and optimizing military strength with military operations, Gu Yanzhou used "geometry" as his blade and "data" as his armor. In the war smoke of Liaodong in the late Ming Dynasty, he started a scientific defense revolution that subverted the tradition and turned the tide.
