《旧唐书·列传·卷五十三》
如果以疲惫之师攻其坚固的城池，必将被敌杀死数万人，之后战事才能完成。
若顿兵坚城之下，必死者数万，然后事可图也。
If we attack its strong city with exhausted troops, tens of thousands of people will be killed by the enemy, and only then can the battle be concluded.