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 when we saw them relaxing their hostility to the Persians and eager for the enslavement of the allies, we were no longer without alarm. And the allies, being unable, on account of the number of those who had votes, to unite for self-defence, were all enslaved except ourselves and the Chians;
while we shared their campaigns as presumably “independent” and enjoying at least the name of freedom. And we could no longer regard the Athenians as trustworthy leaders, taking as warning examples the events of the past;
for it was not likely that they, after subjugating those with whom they had entered into treaty relations together with us, would not do the same to those who were left, if ever they should possibly have the power.
"Again if we had all remained independent we should have had better assurance that they would make no violent change in our status; having, however, the majority under their hands, while still associating with us on an equal footing, they would naturally find it more irksome that our state alone still maintained its equality as compared with the majority that had already yielded, especially since they were becoming more powerful in proportion as we became more isolated.
Indeed it is only the fear that arises from equality of power that constitutes a firm basis for an alliance; for he that would transgress is deterred by the feeling that he has no superiority wherewith to make an attack.
And we were left independent for no other reason than because they clearly saw that with a view to empire they must get control of affairs by fair-seeming words and by attacks of policy rather than of force.
For, on the one hand, they had as evidence in their favour that surely those who have an equal voice with themselves would never have taken part in their campaigns had not those whom they attacked been guilty of some wrong; and on the other hand, they also brought the united strength of the strongest states against the less powerful first, and leaving the former to the last they counted upon finding them weaker when all the rest had been removed from around them.