Battle of Baideng (200 BC): Han Emperor Gaozu Besieged by Modu

The Battle of Baideng was a campaign in the winter of 200 BC in which the Xiongnu ruler Modu Chanyu surrounded Emperor Gaozu, founder of the Han dynasty, on a hill near Pingcheng in northern China. Gaozu was trapped for seven days and escaped only through negotiation. The humiliation convinced the Han court that it could not defeat the steppe nomads by force, and it adopted the heqin policy of marriage alliances and tribute-like gifts that lasted for some 65 years.

Background

While China was torn by the civil wars that ended at the Battle of Gaixia in 202 BC, a new power rose on the steppe to the north. Modu, son of the Xiongnu chief Touman, killed his father around 209 BC and took the title chanyu. He crushed the Donghu to the east, drove back the Yuezhi to the west and united the nomadic peoples of the Mongolian plateau into a confederation able to field huge cavalry armies.

The Han empire was barely established. In 201 BC Han Wang Xin, a Han vassal king stationed at Mayi on the northern frontier, was attacked by the Xiongnu and went over to them. He is often called Han Wang Xin to distinguish him from the more famous general Han Xin. His defection opened northern Shanxi to invasion, and Gaozu decided to lead an army against Modu in person.

The campaign and the siege

Gaozu marched north in the bitter winter of 200 BC. Sima Qian writes that the cold and snow were so severe that two or three in every ten soldiers lost fingers to frostbite. The army was mostly infantry, and the traditional figure of 320,000 men is probably exaggerated.

Modu set a trap. He hid his best troops and let Han scouts see only weak men and thin animals. Gaozu’s envoys reported that the Xiongnu could be attacked, except for one, Liu Jing (originally named Lou Jing), who warned that the display was a ruse. Gaozu had him arrested and pushed ahead with a vanguard to Pingcheng, far in front of his slow-moving infantry.

Modu then surrounded the emperor on Baideng, the “White Mount”, near Pingcheng. Sima Qian claims the chanyu had 400,000 cavalry, grouped by the colour of their horses on each side of the hill. The number is surely inflated, but the encirclement was real. For seven days Gaozu’s men were cut off from the main army and from supplies.

The escape

Gaozu’s adviser Chen Ping devised a way out. Sima Qian calls it a secret plan and gives only part of it: envoys carried lavish gifts to Modu’s consort, who urged her husband to withdraw. She reportedly argued that even if Modu took Han lands he could not live in them, and that the Han ruler also had divine protection.

Modu had his own reasons for caution. Han Wang Xin’s generals, who had agreed to join him, had not arrived, and he began to suspect them of plotting with Han. He opened one corner of the encirclement. Gaozu’s men walked out with their crossbows drawn and arrows pointing outward, and reached the main army. Modu then withdrew.

Consequences: the heqin policy

Gaozu released Liu Jing, apologised and rewarded him with a marquisate. Liu Jing then proposed the policy that would define Han-Xiongnu relations for two generations. Han would send a princess to marry the chanyu, along with annual gifts of silk, wine and grain, and the two rulers would treat each other as brothers.

The first heqin agreement was made around 198 BC. Empress Lü refused to let her own daughter go, so a young woman of the imperial clan was sent instead with the title of princess. Later rulers renewed the treaties with larger gifts, and the two states agreed to treat the Great Wall as the frontier between them.

The policy did not stop raids, and Modu even sent Empress Lü an insulting letter around 192 BC proposing marriage. Remembering Pingcheng, her ministers advised against war, and she replied humbly. Heqin lasted until 133 BC, when Emperor Wu abandoned it with a failed ambush at Mayi and began decades of war that culminated in the Battle of Mobei in 119 BC.

Myths and facts

Myth: Chen Ping’s trick was to show Modu’s consort a portrait of a beautiful Chinese woman. Later Han writers speculated that Chen Ping showed the consort a picture of a beautiful woman and hinted that Han would send such women to replace her in the chanyu’s favour. Sima Qian, the earliest source, says the plan was kept secret, so its details are unknown.

Fact: The numbers are not reliable. The armies of 320,000 and 400,000 men come from Sima Qian’s account and are generally regarded as exaggerations, though both forces were clearly large.

Timeline

• c. 209 BC: Modu kills his father Touman and becomes chanyu of the Xiongnu.
• 202 BC: Liu Bang defeats Xiang Yu and becomes Emperor Gaozu of Han.
• 201 BC: Han Wang Xin surrenders Mayi to the Xiongnu.
• 200 BC, winter: Gaozu marches north; Modu besieges him at Baideng for seven days.
• c. 198 BC: First heqin treaty; a Han imperial bride is sent to Modu.
• c. 192 BC: Modu’s insulting letter to Empress Lü; Han avoids war.
• 133 BC: The Mayi ambush ends the heqin era.

Why it matters

Baideng showed that the new Han empire could not match the Xiongnu cavalry on the steppe. The heqin policy that followed gave Han decades to recover its strength, and the memory of the siege shaped Chinese frontier thinking until Emperor Wu of Han turned to all-out war.