The Battle of Fei River ( 淝水之战 ) was a battle in 383, where Fu Jian ( 符坚 ) of the Former Qin ( 先秦 ) was decisively defeated by the numerically inferior army of Eastern Jin ( 东晋 ) . The battle is considered to be one of the most significant battles in the history of China , with the far-reaching consequences of postponing the unification of China by more than two hundred years. The aftermath of the battle includes the Former Qin empire falling into massive civil war and its eventual destruction, ensuring the survival of Eastern Jin and other regimes south of the Yangtze River .

The state of Former Qin, lead by ethnic Di ( 氐 ) tribesman, rose rapidly from a string of successes in the 350s. Fu Jian, nephew of the founder, was a vigorous leader of tremendous drive and ambition. In 370 he conquered the state of Former Yan and in 373 seized almost all of Sichuan from the Jin. In 379, the strategically important city of Xiangyang ( 襄阳 ) , gateway to the Middle Yangtze fell to Qin. By 381, he had united all of north China and was preparing for an invasion of the south.

In the summer of 383 a Jin army attempted to recover Xiangyang but was driven off by a Qin relief column of 50,000 men. According to the "Chronicle of Fu Jian" in Jin shu , Fu Jian responded in the eighth month with an army of 270,000 cavalry, 600,000 infantry and 30,000 elite guards ( 羽林郎 ) , marching from Chang'an. Separate columns were to push downstream from Sichuan but the main offensive would occur against the city of Shouchun on the Huai River . The Jin emperor Sima Yao ( 司马曜 ) hurriedly made preparations for defense. He gave Huan Chong ( 桓冲 ) responsibility for the defense of the Middle Yangzi. The pressing defense of the Huai River was given to Xie An ( 谢安 ) , Xie Xuan ( 谢玄 ) and the veteran 80,000-strong Beifu Army ( 北府兵 ) .

Knowing that the Jin army was short of men, Fu Jian wanted to seize this opportunity of being much more numerous in armed forces to stage a quick attack. Unexpectedly, the van of Fu Jian's army of 250,000 troops was defeated in the Shouchun city by an ingenious military move of the Jin army and suffered heavy losses. The senior general of the van of Fu Jian's army was killed, and there were heavy casualties of more than 10,000 soldiers. Fu Jian's army was dispirited and its morale was shaken. Many soldiers were in such a great panic that they waited for opportunities to run away. Standing on the city wall of the Shouchun City , Fu Jian and his brother Fu Rong saw that the ranks of the Jin army were in good order and that the morale of the Jin army was high. Turning to his brother, Fu Jian said, "What a powerful enemy this is! Why did people say that the Jin army was short of men?" He deeply regretted that he had taken the enemy too lightly. Overshadowed by the disastrous defeat, Fu Jian ordered his troops to be deployed in battle formation on the north side of the Fei shui River , in an attempt to regain the initiative by relying on the superior geographical conditions. Then Xie Shi and Xie Xuan the senior generals of the Jin army, suggested that Fu Jian's army retreat a little bit, leaving some space, so that the Jin army could cross the river to conduct operations. Fu Jian thought that his chance had come; believing that the senior generals of the Jin army did not have the elementary knowledge of warfare. It was his plan to stage a sudden attack while the troops of the Jin army was busy crossing the river, and he was sure that his plan would word.