The protagonist Chen Yan is an engineering student majoring in mechanical engineering + materials engineering in the 21st century. He is good at mechanical design, material processing, and simple equipment research and development. He is familiar with basic physics, chemistry, and medical knowledge. He has a rational and calm personality, is tough and pragmatic, and has a sense of family and country. He travels to the 17th year of Kaiyuan (the peak of the Tang Dynasty). The border was not peaceful) and became a low-level auxiliary soldier of Fengzhou Qinggang Fortress. Relying on modern engineering knowledge, he went from self-rescue to rescuing his comrades, from improving ordnance to building fortifications, and grew from a grassroots soldier to a generation of famous military officials who guarded the border and assisted the court. He witnessed and participated in the stability of the border and the revolution of military industry in the prosperous Tang Dynasty.
