《汉书·传·郦陆朱刘叔孙传》
局势没有变动则可以防备匈奴，诸侯若叛乱，也足可以率领他们向东讨伐。
无事，可以备胡；诸侯有变，亦足率以东伐。
Even if the current political situation does not change, they will serve as a buffer against the Xiongnu. If any of the feudal lords rebel, we will have more than enough men to pacify them.