History of the Peloponnesian War

And Greece being now in great danger, the leading of the Grecians that league in that war was given to the Lacedaemonians, as to the most potent state. And the Athenians, who had purposed so much before and already stowed their necessaries, at the coming in of the Medes went a ship-board and became seamen. When they had jointly beaten back the barbarian, then did the Grecians, both such as were revolted from the king and such as had in common made war upon him, not long after divide themselves into leagues, one part with the Athenians and the other with the Lacedaemonians, these two cities appearing to be the mightiest, for this had the power by land and the other by sea.

But this confederation lasted but awhile; for afterwards the Lacedaemonians and the Athenians, being at variance, warred each on other together with their several confederates. And the rest of Greece, where any discord chanced to arise, had recourse presently to one of these. In so much that from the war of the Medes to this present war being continually [exercised] sometimes in peace sometimes in war, either one against the other or against revolted confederates, they arrived at this war, both well furnished with military provisions and also expert because their practice was with danger.

The Lacedaemonians governed not their confederates so as to make them tributaries but only drew them by fair means to embrace the oligarchy convenient to their own policy. But the Athenians, having with time taken into their hands the galleys of all those that stood out (except the Chians and Lesbians), reigned over them and ordained every of them to pay a certain tribute of money. By which means their own particular provision was greater in the beginning of this war than when, in their flourishing time the league between them and the rest of Greece remaining whole, it was at the most.