The Battle of Fei River, also known as the Battle of Feishui (), was a battle in AD 383 in China, where forces of the Di-led Former Qin dynasty was decisively defeated by the outnumbered army of the Eastern Jin dynasty. The location of the battle, the Fei River, no longer exists but is believed to have flowed through modern Lu'an, Anhui, near the Huai River. The battle is considered to be one of the most significant battles in Chinese history. In the aftermath of the battle, the Former Qin fell into a massive civil war, resulting in its eventual collapse, ensuring the survival of Eastern Jin and subsequent Han-ruled regimes south of the Yangtze River. Background The state of Former Qin, led by ethnic Di (氐) tribesmen, rose rapidly from a string of successes in the 350s. Fu Jiān, the nephew of the founder Fu Jiàn, was a vigorous leader of tremendous drive and ambition. In 370 he conquered the state of Former Yan and in 373 seized modern Sichuan and Chongqing from Jin. In 379, the strategically important city of Xiangyang, gateway to the Middle Yangtze, fell to Qin. By 381, he had conquered all of north China and was preparing for an invasion of the south. In May 383, a Jin army of 100,000 commanded by Huan Chong attempted to recover Xiangyang but was driven off by a Qin relief column of 50,000 men. In response, Fu Jiān ordered a general mobilization against Jin: 6 of every 10 able-bodied men were conscripted, and 30,000 elite guards (羽林郎) were gathered. In August 383, Fu Jiān sent his brother, Fu Rong, the Duke of Yangping (who had opposed the campaign), with an army of 300,000 as the advance force. Later that month, Fu Jiān marched with his army of 270,000 cavalry and 600,000 infantry from Chang'an. In September, Fu Jiān reached Xiangcheng. Separate columns were to push downstream from Sichuan, but the main offensive would occur against the city of Shouchun on the Huai River. Emperor Xiaowu of Jin hurriedly made preparations for defense. He gave Huan Chong responsibility for the defense of the Middle Yangtze. The pressing defense of the Huai River was given to Xie Shi (謝石) and Xie Xuan (謝玄) and the elite 80,000-strong Beifu Army (北府兵). Prime Minister Xie An oversaw overall strategy. Former Qin Army Fu Jiān's force was composed of many smaller armies