Chong'er is the son of Duke Xian of Jin.Duke Xian of Jin had a favorite concubine named Li Ji.Li Ji wanted to make her own son Xi Qi the crown prince, so she conspired to kill the original prince Shen Sheng, and then tried to use another trick to get rid of the son Chonger and Yiwu, another son of Jin Xiangong.When Chonger and Yiwu heard the news, they both fled abroad for refuge.Chong Er has been to many countries in exile.When he arrived in Chu State, King Cheng of Chu received him as a distinguished guest.At a banquet, King Cheng of Chu asked Chonger: "If the son returns to Jin and becomes the king, how will he repay me?" Chong'er pondered for a while, and said, "I think, if I can return to Jin, I will become king." My lord, if there is a war between Jin and Chu in the future, I will definitely tell the Jin army to "retreat three houses" (in ancient times, one house was 30 miles, and three houses were 90 miles). If the Chu army still refuses to stop fighting, I have to hold it in my left hand. Whip and bow, with a quiver on your right shoulder, I have challenged you."

Chong'er was in exile for 19 years, and finally returned to the state of Jin and became the king of the state, that is, Duke Wen of Jin.Duke Wen of Jin has grown his knowledge and talents after a long period of life in exile. After he ascended the throne, he governed the country with heart, and Jin soon became strong.He is determined to expand outward and strive to be the overlord of the princes.When Duke Wen of Jin wanted to be the overlord, he first clashed with the powerful state of Chu, because King Cheng of Chu wanted to expand outwards and wanted to be the overlord too.