《资治通鉴·唐纪·唐纪三十三》
在常山郡所召募的士卒都是一帮乌合之众，难以抵挡叛军，所以应该深沟高垒，以逸待劳，不要与叛军的精锐直接交锋。
此郡应募乌合，难以临敌，宜深沟高垒，勿与争锋。
The men that you recruited in Changshan county are all rabble, and will not be able to withstand the rebel army, so you should stick to your fortified defenses and rest and recuperate, and not go and clash directly with the rebel's crack troops.