This trench, between 15 and 20 metres 49 and 66 feet in width and depth, proved an effective defence, but in the Tanguts caught the Song patrollers off guard and filled the trench to cross the Old Wall. Despite high tensions between the Xin and the Xiongnu resulting in the deployment ofmen on the Great Wall, no major fighting broke out beyond minor raids.
Emphasizing the poets' loneliness and longing for home while hinting at the pointlessness of their posts, these frontier verses are characterized by imagery of desolate landscapes, including the ruins of the now-neglected Great Wall—a direct product of Tang's frontier policy.
In as many asmen are recorded as involved in the construction.
Workers built brick and cement factories with local materials near the wall. Sand was used as a fill material between reed and willow layers.
There are no surviving historical records indicating the exact length and course of the Qin walls. Construction of the wall started in BC and the existing sections date back to BC. Where natural barriers like ravines and rivers sufficed for defence, the walls were erected sparingly, but long fortified lines were laid where such advantageous terrains did not exist.
For the first time, kiln-fired bricks were used in the construction see the brick-firing kiln in the photo above.