Meanwhile, the Northern Zhou regent Yuwen Hu had sent the official Yin Gongzheng (尹公正) to offer peace in return for his mother Lady Yan and his aunt (the younger sister of his father Yuwen Hao (宇文顥) and uncle Yuwen Tai). Emperor Wucheng, fearful that Northern Zhou and Tujue would launch another attack, agreed, and first sent Lady Yuwen to Northern Zhou. However, he initially detained Lady Yan and had her and Yuwen Hu exchange letters, trying to extract promises from Yuwen Hu. Despite Duan's suggestion that he negotiate formal concessions, Emperor Wucheng, in fear of Yuwen Hu's anger, released Lady Yan in fall 564. However, in winter 564, when Tujue launched an attack on Northern Qi's northern provinces, Yuwen Hu, fearful that Tujue would believe that he was duplicitous, launched an attack on Northern Qi anyway, against the key city Luoyang. Around the new year 565, Duan and Gao Changgong (高長恭) the Prince of Lanling defeated Northern Zhou forces sieging Luoyang, and Northern Zhou forces withdrew.