The History of Great Wall of China | Ming and Qing eras

The Chinese were already familiar with the techniques of wall-building by the time of the Spring and Autumn period between the 8th and 5th centuries BC. During this time and the subsequent Warring States period, the states of Qin, Wei, Zhao, Qi, Han, Yan, and Zhongshan all constructed extensive fortifications to defend their own borders. Built to withstand the attack of small arms such as swords and spears, these walls were made mostly of stone or by stamping earth and gravel between board frames.

The state of Qin emerged victorious in 221 BC; its ruler, now the First Emperor of a unified China, intended to centralize rule and prevent the resurgence of feudal lords; in doing so, he

ordered the destruction of the sections of the walls that divided his empire among the former states. To position the empire against the Xiongnu people from the north, however, he ordered the building of new walls to connect the remaining fortificationsalong the northern frontier. "Build and move on" was a central  guiding principle in constructing the wall, implying that the Chinese were not erecting a permanently fixed border.

Transporting the large quantity of materials required for construction was difficult, so builders always tried to use local resources; stone was used in montane areas, while rammed earth was used while building in the plains. There are no surviving historical records indicating the exact length and course of the Qin walls; most of the ancient walls have eroded away over the centuries, and very few sections remain today. Later, the Han, the Northern dynasties and the Sui all repaired, rebuilt, or expanded sections of the Great Wall at great cost to defend themselves against northern invaders. The Tang and Song dynasties did not undertake any significant effort in the region. Dynasties founded by non-Han ethnic groups also built border walls: the Xianbei-ruled Northern Wei, the Khitan-ruled Liao, Jurchen-led Jin and the Tangut-established Western Xia, who ruled vast territories over Northern China throughout centuries, all constructed defensive walls, albeit being further north—reaching into the environs of present-day Mongolia—than Han-built fortifications.

Ming and Qing eras –

Main article: Ming Great Wall :

The Ming dynasty made substantial contributions to the Great Wall, following their defeat to the Oirats in the Battle of Tumu. This defeat had come in the context of protracted conflict with Mongol tribes; a new strategy for defense was thus realized by constructing walls along the northern border of China. Acknowledging the Mongol control established in the Ordos Desert, the wall followed the desert's southern edge, instead of incorporating the bend of the Yellow River.

Unlike the earlier fortifications, the Ming construction was stronger and more elaborate, due to the use of bricks and stone instead of rammed earth. Up to 25,000 watchtowers are estimated to have been constructed on the wall. As Mongol raids continued periodically over the years, the Ming devoted considerable resources to repair and reinforce the walls; sections near the Ming capital of Beijing were especially strong. Under general Qi Jiguang's supervision, 1 ,200 watchtowers from Shanhaiguan Pass to Changping were constructed between 1567 and 1570, and sections of the ram-earth wall were faced with bricks.

During the mid—15th century, the Ming also built a so-called "Liaodong Wall". It enclosed the agricultural heartland of the Liaodong province, protecting it against potential incursions by Jurchen-Mongol Oriyanghan from the northwest and the Jianzhou Jurchens from the north. While stones and tiles were sometimes used here, it was otherwise simply an earth dike with moats on both sides.

Towards the end of the Ming, the Great Wall helped defend the empire against the Manchu invasions that began around 1600. Even after the loss of all of Liaodong, the Ming army held the heavily fortified Shanhai Pass, preventing the Manchus from conquering the Chinese heartland. The Manchus were finally able to cross the Great Wall in 1644, after Beijing had already fallen to Li Zicheng's short-lived Shun dynasty. Before this time, the Manchus had crossed the Great Wall multiple times to raid, but this time it was for conquest. The gates at Shanhai Pass were opened on May 25 by the commanding Ming general, Wu Sangui, who formed an alliance with the Manchus, hoping to use the Manchus to expel the rebels from Beijing. The Manchus quickly seized Beijing instead, and eventually defeated both the Shun dynasty and the remaining Ming resistance, consolidating the rule of the Qing dynasty over all of China proper.

Under Qing rule and the annexation of Mongolia into the empire, China's borders extended beyond the Great Wall; work on it for the purpose of border defense was thus discontinued. Construction nevertheless persisted with projects like the Willow Palisade; following a line similar to that of the Liaodong Wall of the Ming, it was meant to prevent Han Chinese migration into Manchuria.