Cao Cao and Yuan Shao were heading toward a direct confrontation since the late 190s, and the first months of 200 saw the opening of hostilities at the Battle of Boma after years of manoeuvring. With a feint, Cao Cao was able to split off Yuan Shao's main force gathered at Liyang (黎陽; northwest of present-day Xun County, Henan) across the river from Boma (白馬; near present-day Hua County, Henan) and hence relieve the siege at Boma, killing Yuan Shao's attacking general Yan Liang. Considering that the position at Boma was unsuitable for a determined defence, Cao Cao voluntarily abandoned the outpost and evacuated its population and supplies to the west along the river. With that, Yuan Shao finally crossed the Yellow River in pursuit of Cao Cao's baggage train. However, Cao Cao was not satisf