刘武周
Li Yuan made both Li Jiancheng and Li Shimin key generals, and in nine days they captured Xihe Commandery (西河, roughly modern Lüliang, Shanxi), impressing their father. Subsequently, Li Yuan divided his forces into six armies, giving Li Jiancheng and Li Shimin command of three armies each. He also made Li Jiancheng the Duke of Longxi and Li Shimin the Duke of Dunhuang. Li Yuan then advanced toward Chang'an. As he approached Hedong, torrential rains prevented his army from advancing further. With rumors running rampant that Liu Wuzhou and the Eastern Tujue were about to attack Taiyuan, Li Yuan initially ordered a retreat back to Taiyuan. However, Li Jiancheng and Li Shimin argued that this would mean sure defeat, and Li Yuan changed his mind.