Construction of the Jin Dynasty's Southern Defense Line

Timeline

1. 1215Kaifeng · Kaifeng CityUpon learning of the loss of Zhongdu, Emperor Xuanzong of Jin convened generals at Kaifeng to discuss defense, ordering large-scale conscription of laborers across Henan and Shandong to repair city walls, and gathering scattered routed soldiers from Hebei to march south and form new defensive corps.
2. 1215Along the Yellow River · Yellow River–Huai River BasinThe Jin army focused on strengthening Yellow River ferry crossings and riverside forts, adding garrison troops at Mengjin, Tong Pass, and elsewhere, attempting to use the natural barrier to block Mongol cavalry from advancing south. At the same time, they dredged moats and stockpiled grain and fodder in preparation for a prolonged defense.
3. 1215North of the Huai River · Huai River BasinThe Jin court deployed forces north of the Huai River, guarding both against a Mongol flanking move to the south and against a Northern Expedition by the Southern Song taking advantage of Jin's defeats. Border strongholds such as Suzhou and Sizhou received reinforcements, forming a defensive posture facing both north and south, but with dispersed forces and low morale, the defense line as a whole remained fragile.