《旧唐书》卷110《李光弼传》记:二年,贼将史思明、蔡希德、高秀严、牛廷玠等四伪帅率众十馀万来攻太原。光弼经河北苦战,精兵尽赴朔方,麾下皆乌合之众,不满万人。……乃躬率士卒百姓外城掘壕以自固。作堑数十万,众莫知所用。乃贼攻城于外,光弼即令增垒于内,坏辄补之。其中“作堑数十万”颇觉难解。堑可以指环城之沟壕,即城池,也就是当今所谓的护城河。护城河可以由一条或者数条河沟组成,但其数目决不可能达数十万之多。因此,“作堑数十万”确实难以理解。后来对比《资治通鉴》,才发现该处记载有误。《资治通鉴》卷219肃宗至德二载正月条记: “Old Tang” Volume 110 “Biography of Li Guangbi” Two years, the thief will Shi Siming, Cai Xi De, Gao Xiuyan, Niu Tingxu and other four pseudo-Shuai more than 100,000 people to attack the Taiyuan. Light Bute Hebei war, soldiers do Shuo Fang, all under the command of Wuhe, dissatisfied with the million. ... ... is bow rate soldiers outside the city trench to self-solidition. Hundreds of thousands of grazing, all unknown. Thieves attack outside the city, the light Bute even if by base, the frail make up. Which “for grazing hundreds of thousands ” rather feel puzzled. Catch can refer to the trench city ring, that is, city, which is today the so-called moat. Moat can be composed of one or several river ditch, but its number can never reach as many as hundreds of thousands. Therefore, “grazing hundreds of thousands of” really difficult to understand. Later, compared with “Zi Zhi Tong Jian”, only to find that there is a mistake recorded. “Mirror” Volume 219 Suzong to Germany contained two first-month note: