Inner Mongolia: Great Wall from various periods and the Jin Boundary Trench

The Inner Mongolia autonomous region has the most Great Wall sites in China. It is home to Great Wall remains from the Warring States Period(475-221 BC), the Qin (221-206 BC), Han (206 BC- AD 220), Liao (916-1125), Jurchen-Jin (1115-1234) and Ming (1368-1644) dynasties. The total length of the Inner-Mongolian Great Wall reaches 7,570 kilometers, accounting for nearly one-third of the total length of Great Wall remnants in China.

The earliest Great Wall remnants in Inner Mongolia can be traced back to the sections built by the State of Zhao during the Warring States Period and ensuing Qin Dynasty, China's first unified dynasty. However, these periods were not long or stable enough for the Wall built during this period to be recognized as a complete defense system. It was not until the reign of Emperor Wudi (r. 140-87 BC) of the Han Dynasty that the more complete and "real" Great Wall appeared in what is now Inner Mongolia.

The Great Wall of the Jurchen-Jin Dynasty is also known as the Jin Boundary Trench. This military defense structure was built by the Jurcen Jin people against Mongolian attacks. Trenches and walls that were piled up or rammed by rocks quarried from the trenches are used to impede the Mongolian calvary.

The Jin Boundary Trench is divided into a southern line and a northern line. The northern line was built in the early Jin Dynasty, starting from the southern bank of the Gen River in Inner Mongolia, running westward through Russia and Mongolia and ending at the southern foot of the Khentii Mountains, with a total length of more than 700 kilometers.

The southern line was built in the late Jin Dynasty and is known as "The New Wall of the Mingchang Reign" . It starts from the right bank of the Nenjiang River of Inner Mongolia Daur Autonomous Banner of Morin Dawa in the east and ends at Mountain Daqing in the south of Shangmiaogou in Wuchuan county in the west, with a total length of about 6,500 kilometers.

Both the Jurchen-Jin and the Ming dynasties built their complete Great Wall defense systems in Inner Mongolia. In order to weaken the Mongolian cavalry in the north, the Jurchen-Jin Great Wall mainly used boundary trenches as a means of defense, while the Ming Dynasty Great Wall was more complex, with walls, beacon towers, watchtowers, trenches and many other structures.