Liu Bang ignored Liu Jing's warning about the Xiongnu — then was besieged seven days

In 200 BCE, the Xiongnu under Modu Chanyu invaded the region of Dai. Emperor Gaozu of Han — Liu Bang, the founder of the dynasty — personally led an expedition north. Before the campaign he sent his advisor Liu Jing (then still named Lou Jing) to scout the Xiongnu disposition.

Liu Jing reported what he saw: only old men, emaciated cattle, and weak horses — none of the strength a nomadic army would show. He concluded this was a deliberate deception: the Xiongnu were hiding their best troops and baiting the Han into a trap. Liu Jing urged the emperor to wait and strengthen his position. Liu Bang called him a defeatist and ordered him imprisoned in Guangwu to await execution after the victory.

Eager to engage, Liu Bang drove his cavalry ahead of the infantry. At Pingcheng, Modu surrounded the advance force on Baideng Mountain. For seven days the Han army was cut off — no supplies, no reinforcements, no escape. The emperor survived only by sending a secret envoy to bribe Modu's wife with gold and gifts, who persuaded the chanyu to open a gap in the encirclement. The Han army slipped out in a heavy fog.

Liu Bang returned to Guangwu and immediately released Liu Jing, apologised, and enfeoffed him as Marquis of Guangnei. For the rest of the Han dynasty the northern policy was appeasement — heqin marriage alliances and tribute to the Xiongnu — rather than conquest. The lesson of Baideng was learned, but it had cost the founder of the dynasty his dignity.