In the middle of the Chinese chess board, there is often a gap with the words "Chu River" and "Han Boundary" written on it. What does this mean? Originally, this was to compare chess to the "Chu-Han War" in history. According to historical records, the "Chu River Han Boundary" in the ancient Xingyang Chenggao area, north of Huangzi, west of the Qiao Mountains, east of the plains, south of the Song Mountains, is the battlefield of the successive generations of soldiers and families to revitalize the masses. In 203 BC, Liu Bang sent troops to attack Chu, Xiang Yu was short of food and soldiers, and was forced to put forward the requirement of "dividing the world in the middle, cutting the gap to the west for Han, and the east as Chu", and since then there have been theories of "Chu River" and "Han Boundary".
To this day, on the Guangwu Mountain in Xingyang, there are still two ruins of ancient cities facing each other, the west one is called Hanwang City, and the east is called Bawang City, which is said to have been built by Liu Bang Xiangyu in that year. In the middle of the two cities, there is a large ditch about 300 meters wide, which is what people usually call a chasm.
![The Hongmen Feast had already foreshadowed the final outcome of the Chu-Han war[fig]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)