In winter 617, with a conflict between Li Mi and Zhai intensifying, Li Mi set an ambush for Zhai at a feast held for him, killing him, his brother Zhai Hong (), his nephew Zhai Mohou (), and his strategist Wang Ruxin (). During the ambush, Xu was injured in his neck and nearly died. Li Mi, declared, however, that his intention was only to execute Zhai Rang, and no one other than the Zhai clan was to worry. He personally attended to Xu's injuries, and had Xu, Shan, and Wang Bodang take over Zhai's troops.