On "grass-burning" in Ningxia in Ming dynasty

In order to defend Mongolian invasion,the government of Ming dynasty took a series of measures to strength the defense of the northern border,such as establishing jiu-bian,moving capital to Beijing and building the great wall.Since the year of Yongle,the army of Ming government began to burn grass in border every year.Through the main task of grass-burning was to burn grass,there was a well-conceived system of time,scope and route.The essay makes a study on grass-burning in Ningxia in Ming dynasty.