History of the Peloponnesian War

And as things stand now, never yet were the Peloponnesians more hopeless with regard to us: and even if they are ever so confident, for invading our country indeed they are strong enough, even though we do not undertake the expedition; but with their naval force they cannot hurt us, [though we do undertake it;] for we have a fleet left behind that is a match for them.

On what reasonable argument, then, could we ourselves shrink from it; or on what plea addressed to our allies there could we refuse to succour them? For since we have entered into league with them, we ought to assist them, and not to object that they too have not assisted us. For we united them with us, not that they might come here to help us in their turn, but that by annoying our enemies there they might prevent their coming here to attack us.