History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
we have therefore every reason to expect them to risk a battle, if they have not already set out before we are yet there, at any rate when they see us in their territory laying it waste and destroying their property.
For with all men, when they suffer an unwonted calamity, it is the sight set then and there before their eyes which makes them angry, and when they are angry they do not pause to think but rush into action.
And the Athenians are even more likely than most men to act in this way, since they are more disposed to claim the right to rule over others and to attack and ravage their neighbours' land than to see their own ravaged.
Realising, then, how powerful is the city against which you are taking the field, and how great is the fame, for better or for worse, which you are about to win for your ancestors and for yourselves fiom the outcome, follow wherever your officers lead you, regarding good order and vigilance as all-important, and sharply giving heed to the word of command; for this is the fairest as well as the safest thing—for a great host to show itself subject to a single discipline."
With these words Archidamus dismissed the assembly. He then first sent Melesippus son of Diocritus, a Spartan, to Athens, in the hope that the Athenians, when they saw that the Lacedaemonians were already on the march, might be somewhat more inclined to yield.