History of the Great Wall of China the three, China's chief concern since the earliest times had been Mongolia – the home of many of the country's fiercest enemies including the Xiongnu, the Xianbei, the Khitans, and the Mongols. The Gobi Desert, which accounts for two-thirds of Mongolia's area, divided the main northern and southern grazing lands and pushed the pastoral nomads to the fringes of the steppe. On the southern side (Inner Mongolia), this pressure brought the nomads into contact with China. For the most part, barring intermittent passes and valleys (the major one being the corridor through Zhangjiakou and the Juyong Pass), the North China
Ordos Desert in the south. The Ordos Desert is almost completely encircled by the Great Bend (Ordos Loop) of the Yellow River in the west, north, and east. Mountain ranges separate the Ordos from the Gobi Desert north and east of the Yellow River. The northern border serves as the southern border of the Muu-us Sandyland. The mountain chains separating the Ordos from the central Gobi in the north of the great bend of the Yellow River are: the Kara-naryn-ula, the Sheitenula, and the Yin Mountains, which link on to the south end of the Greater Khingan Mountains. In the south and