sentences:  In 643, in the aftermaths of major conflict between Emperor Taizong's sons Li Chengqian (the Crown Prince) and Li Tai (the Prince of Wei), who was Emperor Taizong's favorite son, causing Li Chengqian to plot to overthrow his father in fear that his father would replace him with Li Tai, Cui submitted a secret petition urging for Li Tai to be made crown prince.Emperor Taizong, after some deliberation, deposed both Li Chengqian and Li Tai, holding Li Tai's machinations responsible for Li Chengqian's downfall, and as Cui had wanted Li Tai made crown prince, he drew Emperor Taizong's ire and was demoted to the post of assistant minister of palace supplies.Later, his post was changed to deputy minister of census.