After Yuan Shao's defeat at Guandu, many cities within his territory north of the Yellow River rebelled and switched allegiance to Cao Cao. Despite this, Cao Cao's forces were too exhausted from the strain of battle to take advantage of the situation. Yuan Shao still retained a presence south of the river at Cangting (倉亭; north of present-day Yanggu County, Shandong), a lone bridgehead down the river east from the battlefields of Guandu.