From Ming Dynasty to Liaodong

In the seventh year of the Apocalypse, Jinzhou was alone behind enemy lines, and its eight hundred remnant soldiers were besieged both inside and outside. Lin Yuan, who came from time traveling, had no plug-ins, no system panels, only a knowledge database and four analysis opportunities per year. He did not serve as an aide to a powerful minister or cling to the powerful officials in the court. He squatted in the military workshop repairing gun barrels, setting standards, refining iron, and turning a dead city into a copper wall. It doesn't depend on luck, just on craftsmanship. Then, he wanted the Jianzhou cavalry to stop outside the pass and the European colonial ships to turn around and return to the sea. Starting from an isolated city, we can turn the entire era back to the direction it should go.