The Chu-Han War took place from 206 BC to 202 BC between Xiang Yu and Liu Bang, both of whom tried to claim power after the collapse of the Qin Dynasty. Both have rebelled against the Qin Dynasty's rule the moment two peasants, Chen Sheng and Wu Guang, rose up. Xiang Yu, on the one hand, was the grandson of a general in the Chu State whilst Liu Bang was the son of a peasant living in the present Jiangsu Province.
It was Liu Bang who first led his army into Xianyang (capital city of the Qin Dynasty) after defeating the Qin's army. According to King Huai's promise, the first to enter Xianyang would be regarded as the King. However, Xiang Yu killed King Huai of the Chu State and proclaimed himself the King of West Chu.
At the same time, tens of kings were designated by him, amongst whom Liu Bang was proclaimed as the King of Han. The latter accepted without objection since he felt inferior to Xiang Yu then. However, Liu Bang built up his power secretly in his land. He developed agriculture and trained soldiers by accepting the advice of his two advisers, Xiao He and Zhang Liang. As a result, his power became stronger and grew very quickly indeed.
Constant battles occurred the following years between Liu Bang and Xiang Yu, with the latter having the advantage at first. However, Liu Bang managed to turn the tide against his enemy because he was good at picking the right person and effective military strategies for the war. Knowing his defeating position, Xiang Yu quickly proposed to divide the country into two with a boundary called Honggou. The western part of Honggou was assigned to Liu Bang (Han) and the east to himself (Chu).
Not long after that, however, the former broke the agreement and Xiang Yu's troop was chased out of the Chu State. Eventually, the latter committed suicide at Wujiang River (the present northeastern part of He County, Anhui Province), thus ending the four years' war. Liu Bang then set up the Western Han Dynasty.