Gansu to the coast of southern Manchuria. Later dynasties adopted different policies towards northern frontier defense. Walls, although they rarely followed Qin’s routes. Although a useful deterrent against raids, at several points throughout its history the Great Wall failed to stop enemies, including in 1644 when the Manchu Qing marched through the gates of Shanhai Pass and replaced the most ardent of the wall-building dynasties, the Ming, as rulers of China. The Great Wall of China visible today largely dates from the Ming dynasty, as they rebuilt much of the wall in stone and brick, often extending its line through challenging terrain.
Topographical map of China’s northern frontier area, with modern political boundaries. Manchuria, unmarked, is to the east of Inner Mongolia. The conflict between the Chinese and the nomads, from which the need for the Great Wall arose, stemmed from differences in geography. The 15″ isohyet marks the extent of settled agriculture, dividing the fertile fields of China to the south and the semi-arid grasslands of Inner Asia to the north. According to the model by sinologist Karl August Wittfogel, the loess soils of Shaanxi made it possible for the Chinese to develop irrigated agriculture early on. The steppe societies of Inner Asia, whose climate favoured a pastoral economy, stood in stark contrast to the Chinese mode of development.
As animal herds are migratory by nature, communities could not afford to be stationary and therefore evolved as nomads. According to the influential Mongolist Owen Lattimore this lifestyle proved to be incompatible with the Chinese economic model. Potential nomadic incursion from three main areas of Inner Asia caused concern to northern China: Mongolia to the north, Manchuria to the northeast, and Xinjiang to the northwest. North China Plain remained shielded from the Mongolian steppe by the Yin Mountains. Although Manchuria is home to the agricultural lands of the Liao River valley, its location beyond the northern mountains relegated it to the relative periphery of Chinese concern.
Xinjiang, considered part of the Turkestan region, consists of an amalgamation of deserts, oases, and dry steppe barely suitable for agriculture. Remnants of the Great Wall of Qi on Dafeng Mountain, Changqing District, Jinan, which was once part of the ancient State of Qi during the Warring States Period. One of the first mentions of a wall built against northern invaders is found in a poem, dated from the seventh century BC, recorded in the Classic of Poetry. Most importantly, the fall of Western Zhou redistributed power to the states that had acknowledged Zhou’s nominal rulership.
The rule of the Eastern Zhou dynasty was marked by bloody interstate anarchy. With smaller states being annexed and larger states waging constant war upon one another, many rulers came to feel the need to erect walls to protect their borders. Of these walls, those of the northern states Yan, Zhao, and Qin were connected by Qin Shi Huang when he united the Chinese states in 221 BC. The Yan wall stretched from the Liaodong peninsula, through Chifeng, and into northern Hebei, possibly bringing its western terminus near the Zhao walls.