 From 1544 to 1549, a defensive building program took place on a scale unprecedented in Chinese history.The project was led by Weng Wanda (翁萬達; 14981552), the Supreme Commander of the Xuan–Da defence area (宣大總督), which was responsible for the Xuanfu, Datong, and Shanxi areas.Troops were re-deployed along the outer line, new walls and beacon towers were constructed, and fortifications were restored and extended along both lines.