History of the Peloponnesian War

And during the whole of this summer there was intercourse indeed between the Athenians and Peloponnesians, but both parties suspected each other, from immediately after the conclusion of the treaty, on the ground of their not mutually restoring the places specified. For the Lacedaemonians, to whose lot it fell first to restore Amphipolis and the other towns, had not done so:

nor did they make their Thrace-ward allies accede to the treaty, nor the Boeotians, nor the Corinthians; though they were continually saying that, in conjunction with the Athenians, they would compel those states to do so, if they would not of their own accord. They also pleaded in excuse the fact of the time not being specified, at which those who did not accede to it were to be considered as enemies to both sides.

The Athenians therefore, seeing none of these things really performed, suspected that the Lacedaemonians had no upright intentions; so that on their demanding back Pylus, they refused to restore it, (nay, they even repented of having given them back their prisoners taken in the island,) and kept the other places, waiting till they, on their part, performed for them what had been arranged.