Ming Great Wall Defense System

Timeline

1. c. 1403–1424Jizhen Great Wall · YanqingAfter the Yongle court moved the capital to Beijing, border walls were repaired and watchtowers and beacon towers added along the Ji, Xuanfu, Datong, and Liaodong lines; the Nine Borders were established under resident generals, and the Great Wall was transformed from a mere barrier into an integrated defense system with the garrisons (large-scale brick-and-stone facing and hollow watchtowers came only in the 16th century, during the Jiajing and Longqing eras).
2. 1431–1440Datong Great Wall · DatongAs Oirat power rose during the Xuande-Zhengtong transition, the court ordered repairs to forts, towers, and beacon stations along the Xuanfu, Datong, and Juyong routes, supplementing firearms and provisions, and the beacon alarm and interior reinforcement mechanisms became routine. The large-scale brick-and-stone facing and hollow watchtower construction of the Ming Great Wall only fully unfolded after the Tumu Crisis (1449), especially in the 16th century; this phase was border-wall repair and watchtower reinforcement, and should not be called 'the last large-scale overhaul before the Tumu Crisis.'
3. c. 1548–1580Mutianyu Great Wall · HuairouQi Jiguang governed Ji from the late Jiajing to early Longqing period, supervising the construction of about 1,200 watchtowers along the Shanhaiguan-Changping line between 1567 and 1570, and facing rammed-earth walls with brick and stone. After the Longqing peace settlement, garrison strength on some sections was adjusted, but the Ji watchtower system became a model of the Ming Great Wall's militarized construction.