History of the Peloponnesian War

"To cope with such a power we need not only a naval armament of such insignificant size, but also that a large force for use on land should accompany the expedition, if we would accomplish anything worthy of our design and not be shut out from the land by their numerous cavalry; especially if the cities become terrified and stand together, and some of the others, besides Egesta, do not become our friends and supply us cavalry with which to defend ourselves against that of the enemy.

And it would be shameful to be forced to return home, or later to send for fresh supplies, because we had made our plans at first without due consideration. So we must start from home with an adequate armament, realizing that we are about to sail, not only far from our own land, but also on a campaign that will be carried on under no such conditions as if you had gone against an enemy as allies of your subject-states over here, where it would be easy to get whatever further supplies you needed from the friendly territory; nay, you will have removed into an utterly alien land, from which during the winter it is not easy for a messenger to come even in four months.