 With the Ordos now adequately fortified, the Mongols avoided its walls by riding east to invade Datong and Xuanfu (宣府; present-day Xuanhua, Hebei Province), which were two major garrisons guarding the corridor to Beijing where no walls had been built.The two defence lines of Xuanfu and Datong left by the Northern Qi and the early Ming had deteriorated by this point, and for all intents and purposes the inner line was the capital's main line of defence.Starting from the 1520s, proposals were made to strengthen the defences of this region, but the plan was disrupted by the local populace's resistance to the prospect of labour; only in the 1540s did work proceed in earnest.