During the Eastern Jin Dynasty, Fu Jian, king of the State of Qin, controlled northern China. In the year383, Fu Jian led 900,000 infantry and cavalry troops to assault the State of Jin which was south of the Yangtze River. Xie Shi and Xie Xuan, senior generals of the Jin army, led 80,000 troops to offer resistance. 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 area 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 Feishui 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 ooperations. 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. So he willingly accepted the suggestion of the Jin army.

Unexpectedly, the moment the order to retreat was given, Fu Jian's troops were utterly routed and could by no means be controlled. Taking advantage of this favorable situation, the Jin army crossed the river, pursuing and attacking the enemy. The trooops of Fu Jian's army threw away everything in headlong flight, and the field was littered with the corpses of the soldiers of Fu Jian's army. Fu Rong was killed in the tangled fighting, and Fu Jian was hit by an  arrow and ran away. The Jin army won a brilliant victory by defeating a big army with its limited armed forces.

This story comes from "The Life of Fu Jian" in the volume "Records" of The History of the Jin Dynasty. The set phrase "every bush and tree looks like an enemy" is subsequently used to refer to a state of extreme nervousness.