The Battle of Huoyi (霍邑之戰; Wade–Giles: Huo-i) was fought in China on 8 September 617,[3] between the forces of the rebel Duke of Tang, Li Yuan, and the army of the ruling Sui dynasty.

[4][5][6] As a result, from 611 on, rural revolts broke out across the empire, and with the Emperor's prestige and legitimacy diminished by military failure, ambitious provincial magnates were encouraged to challenge his rule.

Yang continued to be fixated on the Korean campaigns, and only as unrest spread within the empire and the powerful Eastern Turks turned hostile, did he realize the gravity of the situation: in 616, he abandoned the north and withdrew to Jiangdu, where he remained until his assassination in 618.

A scion of a noble family related to the Sui dynasty and with a distinguished career behind him, Li Yuan was an obvious candidate for the throne: his province possessed excellent natural defenses in the form of the Taihang Mountains, a heavily militarized population, and was located near the imperial capitals of Daxingcheng (Chang'an) and Luoyang.

In reality, as revealed by the diary of his chief secretary, Wen Daya, Li Yuan was considering a rebellion at least by the time of his appointment to Taiyuan in early 617, and was very much the driving force behind the revolt.

He also concluded an alliance with Shibi, the powerful qağan of the Eastern Turks, which secured his northern frontier from a Turkish invasion and provided him with men and, most importantly, horses, which he lacked.

His 'righteous army' comprised 30,000 men, raised from the local 'soaring hawk' militia, but with some 10,000 additional volunteers, and including a 500-strong Turkish contingent provided by the qağan along with 2,000 horses.

A small force under Zhang Lun was detached to advance parallel to the main army and captured the loyalist commanderies further west, securing the flanks.

[16][19] Li Yuan's advance was stopped at a place called Guhubao for two weeks in late August due to heavy rainfall, giving time to the Sui authorities to react.

Huoyi was placed on the southern exit of a defile through which the road passed, following the course of the Fen River, and provided an excellent position from which to check an army coming from the north.

When Li Yuan's army learned of Song Laosheng's presence, some began advocating a retreat to Taiyuan, fearing that in their absence the Turks might break the treaty and attack it.

[22][23] According to Wen Daya, Li Yuan feared that Song Laosheng would deny battle and instead force him to engage in a prolonged and costly siege of the town.

[12][29] The new dynasty still had to face the various local rebels and warlords that had sprung up throughout the Chinese Empire, but by 628, with a judicious mixture of force and clemency, the Tang had succeeded in the pacification and consolidation of China under their rule.