2. Waging War
It is only one who is thoroughly acquainted with the evils of war that can thoroughly understand the profitable way of carrying it on.
That is, with rapidity. Only one who knows the disastrous effects of a long war can realize the supreme importance of rapidity in bringing it to a close. Only two commentators seem to favor this interpretation, but it fits well into the logic of the context, whereas the rendering, "He who does not know the evils of war cannot appreciate its benefits," is distinctly pointless.