Battle of Qian Shui Yuan

The Battle of Qian Shui Yuan (浅水原之战) was a battle fought in Qian Shui Yuan (in modern-day the north-west of Changwu, Shaanxi 陕西长武东北) in 618 AD—during the Tang Dynasty. The battle ended in the victory of the Tang Dynasty, whose armed forces were led by Li Shimin (李世民).

Background
In 618 AD, Xue Ju (薛举), who occupied in Longxi (陇西) and capitaled in Tianshui (天水), in modern-day Gansu (甘肃), entitled himself as the Qing Emperor (秦帝). He was possessed with an army of 300,000 soldiers and tended to capture Chang'an (长安).

The Battle
In 618 AD, Li Yuan, Emperor Gaozu of Tang (李渊，唐高祖), appointed Li Shimin as the marshal to meet head-on. At first, they were defeated in Qian Shui Yuan and forced back to Chang An. Gao Zhi (高墌) was annexed. After Xue Ju's death, his son Xue Rengao (薛仁杲) succeeded to the throne and continued to attack the Tang army. Li Yuan tried to get support from Li Gui (李轨), who occupied in Liangzhou (凉州， in modern-day Wu Wei, Gan Su, 甘肃武威). At the same time he ordered Li Shimin to press on towards Gao Zhi. Xue Rengao dispatched the general Zong Luo (宗罗), leading more than 100,000 soldiers to resist. Li Shimin thought the Tang army was frustrated while the enemies were inspiring. So he switched from attacking to defending. The two sides were locked in a stalemate for about 60 days. When the Xue army were short for provisions, Li Shimin took great advantage of physical features of Qian Shui Yuan and started attacking. Finally, Xue army was badly defeated and surrendered. The Tang Dynasty suppressed Long Xi and ensured the safety of Guanzhong (关中).