Battle of Guandu - The Siege of Guandu

The Siege of Guandu

In the eighth month, Yuan Shao's army slowly advanced southward from Yangwu and engaged Cao Cao's men in trench warfare, behind the earthen embankments that both sides made. Both sides harassed each other with engines of war. Yuan Shao had erected siege-ramps and high platforms which allowed his men to rain arrows onto Cao Cao's forces. In response, Cao Cao's men had to carry their shields above their heads, and retaliated with traction trebuchets that destroyed the archer platforms. Yuan Shao also tried to tunnel under Cao Cao's fort, but Cao Cao had a large ditch dug within his lines to block the tunnels. Subsequently, neither side could overcome each other as Cao Cao and Yuan Shao became locked in a stalemate.

Before long, Cao Cao's army began to run short of supplies and Cao Cao was in a dilemma on whether to retreat in order to lure Yuan Shao deeper into his territory. Xun Yu, the defender of the capital Xu, sent Cao Cao a letter dissuading him from retreat. He wrote, drawing historical examples from the Chu–Han Contention:

...your military supplies are low, but they are not as bad as the situation of Chu and Han at Xingyang and Chenggao. At that time neither Liu nor Xiang were willing to be the first to retreat. The first to retreat reveals that his strength is exhausted. You, Duke, with one-tenth of the enemy's force you have held the ground you marked, and gripping him by the throat, have not let him advance for already half a year. In this situation his strength will be exhausted and there must arise some crisis. This is the time for employing unexpected stratagems; you may not miss this opportunity.

Cao Cao followed this advice and held fast to his ground. In the ninth month, Xun Yu pointed out that Yuan Shao had been storing supplies at a depot in the village of Gushi (故市; southwest of present-day Yanjin County, Henan), guarded by Han Meng. Cao Cao sent out small cavalry units led by Xu Huang and Shi Huan (史渙) to attack this position. They succeeded, routing Han Meng, disrupting Yuan Shao's supply lines, and burning his grain carts. Yuan Shao was forced to call for relief supplies in response to this raid.