The battle of Gaixia (January 202 BC) was the decisive battle of the Chu-Han Contention and saw Liu Bang inflict a major defeat on Xiang Yu of Chu, who committed suicide soon after the battle.
In 203 BC Liu Bang and Xiang Yu had agreed to split China between them (Treaty of the Hong Canal), but Liu Bang had almost immediately broken the agreement and turned on Xiang Yu. Liu Bang’s plan required support from his allies, most importantly Peng Yue, a warlord who had supported him earlier in the war and was now premier of Wei, and Han Xan, one of Liu Bang’s generals who had forced Liu Bang to make him King of Qi in the previous year. Neither man turned up, and Liu Bang suffered a heavy defeat at Guling.
Liu Bang responded to this setback by promising both men rewards for taking part in the campaign. Liu Bang’s kingdom was to be expanded towards the coast, and he would also gain the part of Chu that included his home town. Peng Yue was to become King of Wei.
The bribery worked as expected. Han Xan led up to 300,000 men to join Liu Bang, while Peng Yue also brought his army from Wei. To make things worse Zhou Yin, one of Xiang Yu’s generals, betrayed him and joined the Han army at Gaixia (near Suiyang, Henan), as did an army under General Liu Jia. On their way these armies attacked Chengfu and Liu, sacking both places.
By the end of 203 BC Xiang Yu was in a terrible position. He had 100,000 men in his fortified camp at Gaixia, but food was running short. His enemies apparently had 500,000 men, and Xiang Yu’s camp was soon surrounded by three rings of enemy troops.
Overnight the Han army began to sing songs from Chu. Xiang Yu was demoralised by this, apparently believing that his own kingdom had turned against him. A large number of troops deserted at this point, although perhaps not quite as many as some ancient sources, in which all but 800 go, suggest.
Xiang Yu decided to try and break out of the trap. Leading 800 cavalry (probably the inspiration for the above figure) he managed to break through the enemy lines. The Han didn’t realise he had gone until the next morning, giving Xiang Yu a head start. When Liu Bang realised what had happened he sent General Guan Ying and 8,000 cavalry to chase him down. Xiang Yu’s cavalrymen quickly dropped away. By the time he crossed the Huai River only 100 were left, and by the time the Han caught up with him near the Wu River that had dropped to 28. After fighting a number of skirmishes (greatly exaggerated in the ancient sources), Xiang Yu committed suicide just before he could be captured.
With Xiang Yu dead the Chu cause was doomed. The city of Lu held out until Liu Bang arrived with Xiang Yu’s head, and then surrendered. A few months later Liu Bang declared himself to be Emperor, founding the Han Dynasty.