Battle of Yanshi

Map of the situation in China during the transition from the Sui to the Tang, with the main contenders for the throne and the main military operations

Date	5–6 October 618
Location	Yanshi, east of Luoyang
Result	Decisive victory of Wang Shichong. Li Mi's followers join Wang, who soon deposes the Sui puppet Yang Tong and installs himself as emperor.

Belligerents

Sui Dynasty

Li Mi's forces

Commanders and leaders

Wang Shichong

Li Mi

Strength

20,000

ca. 40,000

Casualties and losses

light

heavy, large numbers surrendered

The Battle of Yanshi (偃師之戰) was fought on 5–6 October 618 between the armies of Wang Shichong and Li Mi, rival contenders for the succession of the Sui Dynasty. Wang, who was still ostensibly a Sui loyalist and had been blockaded in Luoyang for months by Li Mi, gambled on a decisive battle and led his troops out to attack the besieging army. Li assembled his forces on a naturally defensible position north of Yanshi town, but Wang managed to surprise Li's forces and approach their camp before they could react. Aided by a secondary cavalry attack from the rear, Wang secured a decisive victory over Li's forces. Although Li managed to escape with part of his army, his authority was shattered, and his followers joined Wang. While Li Mi sought refuge in the rival Tang court, Wang consolidated his control over Henan and eventually deposed the Sui puppet ruler Yang Tong and declared himself as Emperor of the new Zheng dynasty. Wang's power lasted until his surrender to the Tang prince Li Shimin in 621.

During the later reign of the second emperor of the Sui Dynasty, Yang (reigned 604–618), the dynasty's authority began to wane: the immense material and human cost of the protracted and fruitless attempts to conquer the Korean kingdom of Goguryeo, coupled with natural disasters, caused unrest in the provinces, while the successive military failures eroded the emperor's prestige and legitimacy ("Mandate of Heaven") among the provincial governors. Yang nevertheless continued to be fixated on the Korean campaigns, and by the time he realized the gravity of the situation, it was too late: as revolts spread, in 616, he abandoned the north and withdrew to Jiangdu, where he remained until his assassination in 618. Local governors and magnates rose to claim power in the wake of Yang's withdrawal. By the summer of 618, nine major contenders emerged, some claiming the imperial title, others contenting themselves, for the time being, with more modest titles. The three most powerful were Li Yuan, who seized the Sui capital of Daxingcheng (Chang'an) and on 16 June 618 proclaimed himself the first emperor of the Tang Dynasty;Dou Jiande, a one-time bandit leader who had risen in revolt against the Sui already in 611, and came to control most of Hebei as the "King of Changle" and then as the "King of Xia"; and Li Mi in Henan, who led a mixture of rebelled peasants and Sui soldiers.

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