The siege of Yanmen, 615

In the eighth month of 615 the Sui emperor was escaping the summer heat at the Fenyang palace on the northern frontier. Shibi Khan led his tribes down and shut him inside the town of Yanmen.^[1] The commanderies were ordered to send troops to the imperial camp.^[1]

Causes

For a generation the Sui had managed the khaganate by dividing it. They paid one khan against another and married princesses into the Ashina.^[1] Yami Khan, Shibi’s father, had been the client this policy produced. He had held the eastern steppe with Chinese support.^[1]

Shibi inherited that arrangement and did not keep it. The Sui court had gone on working to weaken him after his accession. The siege of 615 was his answer. The client with a hundred thousand horse arrived at the frontier while the emperor was standing on it.

The siege and its end

The Sui Shu tells the end briefly: the relief armies had just arrived when Shibi withdrew.^[1] It gives no battle and no terms. It gives instead the consequence: from that time the tribute ceased.^[1] The khaganate had been a tributary of the Sui since Shibi’s father. The siege ended that relation, and the chapter marks the break at exactly this point.^[1]

The chronicle tradition, not the Sui Shu’s own chapter on the Göktürks, holds the fuller accounts of the weeks inside the town. They tell of the emperor in tears, the promises made to the defenders and afterwards broken, and the report that is said to have drawn the khan away.

Consequences

The siege did not destroy the Sui. It ended them all the same. The chapter’s own summary says so without hedging: the emperor handled the Göktürks in the wrong way, and out of that came the encirclement at Yanmen. Then the bandit risings broke out everywhere at once. From that time the khaganate grew great.^[1] The men who founded the Tang rose as one of those rebellions. They rose with Göktürk horses and Göktürk agreement behind them.

For the khaganate the siege was the high point of its eastern policy. The steppe dictated to a Chinese empire instead of being paid by one. Fifteen years later Ilig, Shibi’s brother, was a prisoner in Chang’an.^[2]