With much internal troubles, Ashina Duobi was unable to aid Liang, and later in 628, with Emperor Taizong's brother-in-law Chai Shao (柴紹) sieging Liang's capital Shuofang (朔方, in modern Yulin, Shaanxi), Liang Shidu's cousin Liang Luoren (梁洛仁) assassinated Liang Shidu and surrendered, ending the final rival claim to Emperor Taizong's for China's imperial throne.
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At the same time, however, Xueyantuo, which had been a vassal of both the Eastern Turkic Khaganate and the Western Turkic Khaganate at times, was beginning to strengthen, as was another vassal of the Eastern Turkic Khaganate, Huige, and Ashina Duobi was unable to defeat or contain them.
Later in the year, Ashina Rangan died, and was succeeded by his son Shibi Khan Ashina Duojishi.
The position of Yabgu was traditionally given to the second highest member of a ruling clan (Ashina), with the first member being the Kagan himself.