In 642, Yi'nan began an attempt to cement his relationship with Tang by sending his uncle Nishou () to Tang to request marriage with one of Emperor Taizong's daughters, offering tributes of horses, mink coats, and a mirror made of amber. Meanwhile, with the Tang general Qibi Heli () -- the chief of the Qibi tribe, a constituent tribe of the Chile as well—being detained in Xueyantuo after he, on a visit back to his tribe, was seized by his own subordinates and taken to Xueyantuo (as his subordinates wanted to submit to Xueyantuo rather than Tang), Emperor Taizong, concerned about Qibi Heli's safety (as Qibi Heli had refused to submit to Xueyantuo, cutting off an ear to show his resolve, causing Yi'nan to nearly execute him), agreed to the marriage proposal, sending the official Cui Dunli to negotiate with Yi'nan the terms, under which Emperor Taizong's daughter Princess Xinxing would marry Yi'nan, in exchange for Qibi Heli's release.