 The work undertaken in this period marked a major shift toward defensive construction.The deterioration of the Ming military position in the steppe transitional zone gave rise to nomadic raids into Ming territory, including the crucial Ordos region, on a level unprecedented since the dynasty's founding.To solve this problem, the Ming could either go on the offensive and re-establish their positions in the steppe, or concede the transitional zones to the nomads and maintain a defensive and accommodative policy.