In the final years of the Qin Dynasty, Emperor Qin II, desperate to cling to power, dispatched the great general Zhang Han with a massive army to brutally suppress the peasant uprisings.
After defeating the rebel forces of Chen Sheng and Wu Guang, General Zhang Han of Qin turned his army against Xiang Liang and Xiang Yu, who had installed King Huai of Chu. Xiang Liang was killed in battle. Arrogant and overconfident, Zhang Han believed the Chu army was no longer a threat and marched to attack Zhao. The Zhao forces were no match for him and were soon besieged at Julu by Zhang Han's subordinates, Wang Li and She Jian.
The King of Zhao, trapped in Julu, sent urgent pleas for help to the rebel armies. Though many answered the call, they all camped ten li away, too afraid to attack the Qin forces.
Meanwhile, King Huai of Chu sent his strategist Song Yi as Supreme General with Xiang Yu as his deputy to lead a relief force. But when Song Yi halted the army for 46 days without moving, Xiang Yu could no longer endure. He killed Song Yi, proclaimed himself Supreme General, and swiftly marched his troops to Julu. Upon hearing this news, King Huai of Chu officially appointed Xiang Yu as Supreme General.
When the Chu army reached the front lines, Xiang Yu charged ahead without a second thought, throwing himself into battle against the Qin forces. Yet the allied troops from over a dozen other camps dared not advance, merely watching from atop their walls. There, the Chu soldiers, led by Xiang Yu, fought as if each man was worth ten, battling with desperate resolve.
After several fierce engagements, the Chu army decisively defeated the Qin forces
After defeating the Qin army, Xiang Yu summoned the allied generals. They all prostrated themselves before him in awe, unanimously acknowledging him as the supreme leader of the rebel forces. With this, Xiang Yu's power swelled rapidly, making him the most formidable force against the mighty Qin.
"The idiom 'watching from the ramparts' originally meant observing others' battle from one's own camp; later used to describe sitting by and watching success or failure without helping either side."
Source: *Records of the Grand Historian*, "Biography of Xiang Yu"
Meaning of the Idiom: Later, the Chinese idiom "作壁上观" came to describe how sitting by and watching success or failure without helping either side.