Hsi Hsia (Xi Xia)
In the 7th century, under pressure from Tibetans, the people known as Tanguts to the Mongols, or Dangxian to the Chinese, migrated east to the Ordos, within a bend in the Yellow River. When the Song came to power in 960, the Tangut seized their opportunity to spread westwards, over the Helan mountains, building their capital near present-day Yinchuan and creating an empire 1500 by 600 km.
The founder of Xi Xia as an independant empire was Li Yuan-hao (declared emperor in 1038). To reinforce this independence he instructed his Tangut men to shave the top of their heads, leaving fringes over their forehead and ears, on pain of death. After 6 years of war with the Song, a treaty was signed whereby the Song were obliged to pay the Tanguts 135,000 rolls of silk, 2 tonnes of silver and 13 tonnes of tea.
In 1209, Xi Xia was the first place that Genghis Khan attacked in his bid to rule the world. The Mongols besieged Yinchuan and tried to flood it. The Tangut emperor submitted to Genghis, handing over tribute and his daugher's hand in marriage. Genghis went off to try his luck with the Chin (Jin) empire and then the rest of the world.
Before his assault on the Khwarezm empire in 1219, Genghis called for troops from his vassals, including the Xi Xia. The emperor's military commander refused Genghis. Retribution came in 1227 when Genghis once again turned his attention to China and the Xi Xia.
Xi Xia's ruler, Xianzong attempted to even the odds by signing treaties with the both the Mongols and the neighbouring Jin. To no avail. The emperor was deposed and Yinchuan was taken. Shortly afterwards Genghis Khan died, but the Mongol hordes carried on regardless, swallowing up Xi Xia and the rest of China.