The treaty of the Hong Canal (203 BC) was a short-lived peace treaty agreed between Liu Bang of Han and Xiang Yu of Chu, in which they agreed to split the old Qin Empire between them. Towards the end of 203 BC the main armies on both sides were facing each other close to Xingyang. Liu Bang had the stronger position and better supplies, but Xiang Yu was the better battlefield commander. Liu Bang also had a second army, under Han Xan, operating in the former kingdom of Qi (north east of Ancient China) from where it threatened Xiang Yu’s northern borders.
In 204 BC, while he was besieged in Xingyang, Liu Bang had offered to split China, with Xiang Yu getting the east and Liu Bang getting the west. At the time Xiang Yu had dismissed this peace offer, but late in 203 BC he agreed to the same terms. The dividing line was to be the Hong Canal (meaning either the Canal of the Flying Geese or Far-Flung Canal), which linked the Yellow River near Kaifeng (east of Xingyang) to the Si River, then a tributary of the Huai River, itself then a major river that ran into sea (the courses of both rivers have since been disrupted by changes in the course of the Yellow River).
The treaty was broken almost as soon as it had been agreed. While Xiang Yu appears to have been happy with its terms, and began the march east back to Chu, Liu Bang (or his advisors) decided that this gave them a chance for an easy victory. Instead of returning home Liu Bang invaded Xiang Yu’s new kingdom, eventually defeating him at Gaixia (202 BC) in the decisive battle of the Chu-Han Contention.