《周书·列传·卷四十九》
以我们没有基地的军队攻打他们严守的堡垒，一旦失败不能攻克，更加助长其气势。
以我悬军攻其严垒，脱一战不克，更成其气。
With our army without a base to attack their heavily guarded fortress, once we fail to conquer it, it will further boost their morale.