History of the Peloponnesian War

For the island called Sphacteria, lying just before and very near to the place, maketh the haven safe and the entries straight, one of them, nearest to Pylus and to the Athenian fortification, admitting passage for no more but two galleys in front; and the other, which lieth against the other part of the continent, for not above eight or nine. The island, by being desert, was all wood and untrodden, in bigness, about fifteen furlongs over. Therefore they determined with their galleys thick set, and with the beak-heads outward, to stop up the entries of the haven.

And because they feared the island, lest the Athenians [putting men into it] should make war upon them from thence, they carried over men of arms into the same and placed others likewise along the shore of the continent.

For by this means the Athenians at their coming should find the island their enemy, and no means of landing in the continent. For the coast of Pylus itself without these two entries, being to the sea harbourless, would afford them no place from whence to set forth to the aid of their fellows; and they in all probability might by siege, without battle by sea or other danger, win the place, seeing there was no provision of victual within it and that the enemy took it but on short preparation.

Having thus resolved, they put over into the island their men of arms out of every band by lot. Some also had been sent over before by turns; but they which went over now last and were left there, were four hundred and twenty, besides the Helotes that were with them. And their captain was Epitadas, the son of Molobrus.