He then effectively forced Emperor Gaozu to first create him crown prince and then yield the throne to him ( as Emperor Taizong ) .
In 626 , Li Shimin ambushed Li Jiancheng and Li Yuanji at Xuanwu Gate and killed them .
Li Shimin then effectively forced Emperor Gaozu to first create Li Shimin crown prince and then yield the throne to Li Shimin ( as Emperor Taizong ) .
In 626 , Li Shimin ambushed Li Jiancheng and Li Yuanji at Xuanwu Gate and killed them .