Later in the year, there was a Tufan incursion, and an army commanded by Guo Ziyi, the deputy supreme commander of the armed forces (in effect, the supreme commander, as Emperor Daizong's son Li Kuo the Crown Prince was the nominal supreme commander) helped to defend Bin Prefecture against Tufan forces. After the Tufan threat subsided, Guo returned to Chang'an, but his forces, under the command of his son Guo Xi (), remained at Bin Prefecture. Guo Xi's soldiers lacked proper discipline and became a major problem for the people of Bin Prefecture, and Bai was troubled but unsure what to do because Guo Xi was Guo Ziyi's son. Duan volunteered to again be discipline officer, and after one month, there was an incident when 17 of Guo Xi's soldiers, in a dispute with a wine seller, killed him and destroyed the winemaking equipment. Duan arrested them and beheaded them. Guo Xi's soldiers were incensed, armed themselves, and got ready to attack Bai's headquarters. Duan went to Guo Xi's headquarters with only one old man attending him. When he arrived there, the soldiers were surprised that he arrived effectively alone. Duan stated, "Why wear your armor for this old soldier? I brought my head with me." He then spoke to them: