《新唐书·列传·卷四十三》
出军袭击，不达到几万人是不能成行的。许多人废弃耕种，而军饷却大大增加，如今年岁欠收，不敷军费，此其二。
出军掩敌，兵不数万，不可以行，废农广馈，饥岁不支，二也。
An expeditionary raid could not start without tens of thousands of men. This would mean many people abandoning their farming, which would hugely increase military spending, and this year the harvest had been poor and military expenses could not be met; this was the second point.