After the Ma Wei mutiny in the 15th year of Tianbao (756), Emperor Xuanzong of the Tang Dynasty fled to Shu in the west and went to Pingliang in the north. At that time, Du Hung-chien discussed with Wei Shaoyou, Lu, Lu and others and said, "Pingliang is not a place to gather troops. If you want to win, you must go to Shuo Fang. If the prince is given priority to, the soldiers of the dragon are gathered and marched into Huihe, and the northern army is forced to ride hard at the same time to quell the chaos in the south, then the two capitals can be recovered, and the national humiliation can be reported, and the wise master and the people can be reported. " Du Hung-chien drafted a charter, stating the military strength of the Northern Army and asking Haan Lee to get to Pingliang. Hengli was overjoyed and decided to go to the north.

Soon, Du Hung-chien greeted Hengli in Baicaotun, north of Pingliang, and while comforting the soldiers, he said to Hengli, "The army of the North is outstanding in the world, and its martial arts are also useful. Now Uighur please make peace, Tubo joins, and all counties and counties refuse to accept thieves. Although some counties were occupied by rebels, they all hoped to return to the imperial court. His Royal Highness will rearm in Shuofang, and then send troops south, which will surely wipe out the rebels. " Hengli was impressed by this. On July 9 of the same year, Hengli arrived at Lingwu, the base camp of the Northern Army, accompanied by Du Hung-chien and others.