Battle of Guandu

As the Han dynasty disintegrated, two warlords emerged as the strongest in northern China: Yuan Shao, who held the north with a large army, and Cao Cao, who controlled the Han emperor himself. In 200 Yuan Shao marched south, and the armies faced each other for months across fortified lines at Guandu, near the Yellow River, while Cao Cao's supplies ran low. A defector from Yuan Shao's camp told Cao Cao where his rival's grain was stored, at Wuchao, and Cao Cao led a night raid that burned it. Yuan Shao's army fell apart, and by the traditional account he escaped north with only a small escort. The victory made Cao Cao master of northern China.

Some historians treat Guandu, rather than the more famous battle fought eight years later, as the battle that settled the shape of northern China for a generation. The traditional army sizes look designed to magnify Cao Cao's achievement, and some modern scholars argue the two sides were much closer in strength. One detail recorded in the early sources became a lesson in statecraft: after the victory Cao Cao found letters in which his own officers had corresponded with Yuan Shao, and he is said to have burned them unread. The site's exact location near the shifting old course of the Yellow River is still discussed.