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.

But if they had begun with us, while the whole body of allies were not only still strong in their own strength, but also had a leader to rally to, they would not have got the mastery so easily.

Besides, our navy caused them some fear, lest it should some day be augmented by being united either with yours or another's and thus become a menace to themselves.