In 729, when there was a Khitan and Kumo Xi incursion, Li Jun was put in titular command of the army sent to repel the Khitan and the Xi, with Emperor Xuanzong's second cousin Li Hui () the Prince of Xin'an in actual command of the army. After Li Hui defeated the Khitan and the Xi, Li Jun was nevertheless rewarded with the honorific title of "Situ" (), one of the Three Ducal Ministers. In 735, his name was changed to Li Yu.