 In 607, when Emperor Yang visited the submissive Qimin Khan of the Eastern Turkish Khaganate ("Tujue"), Empress Xiao accompanied him and she personally visited the tent of the khan's wife Princess Yicheng, who was a daughter of a Yang clansman.In 615, when Emperor Yang and Empress Xiao were touring the northern frontier, Qimin Khan's son and successor Shibi Khan launched a surprise attack against Yanmen Commandery in reprisal against various offenses by the emperor.Princess Yicheng sent the imperial couple advanced warning of her new husband's plans, and they were able to reach the well-fortified commandery seat at present-day Daixian in Shanxi.