brother. Yeon Namsaeng sent his son (later known as Cheon Heonseong/Quan Xiancheng (), as Yeon Namsaeng changed his family name from Yeon () to observe naming taboo for Emperor Gaozu, whose personal name was the same character) to Tang to seek aid. Emperor Gaozong and Empress Wu saw this as the opportunity to destroy Goguryeo, and he initially commissioned Qibi Heli to aid Yeon Namsaeng, and also sent the generals Pang Tongshan () and Gao Kan () to attack Goguryeo. Meanwhile, Empress Wu's sister, the Lady of Han (who had married the low-level official Helan Yueshi ()), and her daughter Lady Helan had both been frequently visiting the palace and were said to be "favored" by Emperor Gaozong. When Lady of Han died in 666, Emperor Gaozong created Lady Helan the Lady of Wei, and wanted to let her live in the palace, but hesitated because he thought Empress Wu would be jealous. When Empress Wu heard this, she was indeed jealous, and therefore she poisoned meat offered by her nephews Wu Weiliang () and Wu Huaiyun (), who had been on poor relations with her and whose grandmother were not her mother Lady Yang; she then gave the poisonous meat to Lady Helan, who ate it and died. Empress Wu then implicated Wu Weiliang and Wu Huaiyun in Lady Helan's death and executed them. Around the new year 667, Emperor Gaozong and Empress Wu further commissioned Li Ji to be the overall commander of the attack on Goguryeo, assisted by Hao Chujun. In fall 667, Li Ji crossed the Liao River and captured Sinseong (新城, in modern Fushun, Liaoning). The Tang forces thereafter fought off counterattacks by Yeon Namgeon and joined forces with Yeon Namsaeng, although they were initially unable to cross the Yalu River. In spring 668, Li Ji turned his attention to Goguryeo's northern cities, capturing the important city Buyeo (扶餘, in modern Siping, Jilin). In fall 668, he crossed the Yalu and put Pyongyang under siege. Yeon Namsan and King Bojang surrendered, and while Yeon Namgeon continued to resist in the inner city, his general, the Buddhist monk Shin Seong () turned against him and surrendered the inner city to Tang forces. Yeon Namgeon tried to commit suicide, but was seized and treated. This was the end of Goguryeo, and Tang annexed Goguryeo into its territory, with Xue Rengui being put initially in charge of former