History of the Peloponnesian War

So the ships sailed with all speed, according to the orders of Demosthenes; while the Lacedaemonians prepared to assault the place both by land and sea, hoping easily to take a building completed in haste, and with only a few men in it.

At the same time, expecting the arrival of the Athenian fleet from Zacynthus to its relief, they intended, in case of their not having taken it before, to bar also the entrances into the harbour, that the Athenians might not be able to come to anchor in it.

For the island that is called Sphacteria both secures the harbour, by stretching in a line with it, and close off it, and narrows its entrances; on one side, near the Athenian fortifications and Pylus, leaving a passage for two ships; on the other, towards the rest of the mainland, for eight or nine. It was all woody and pathless from its desert condition, and in extent about fifteen stades. The entrances then they intended to bar with a close line of vessels, with their heads looking outwards;

while fearing this island, lest the enemy should carry on their operations against them from it, they conveyed over some heavy-armed troops into it, and posted others along the mainland.

For so they thought that both the island would be unfavourable to the Athenians, and the mainland also, as it did not afford any landing-place; for the shores of Pylus itself outside the inlet, looking towards the open sea, would present no ground from which they might proceed to the aid of their countrymen; and so they should storm the place, in all probability, without the risk of a sea-fight, as there were no provisions in it, and it had been occupied after short preparation.