History of the Peloponnesian War

His idea was by their size and thickness to keep off the attacks of an enemy; he thought that they might be adequately defended by a small garrison of invalids, and the rest be freed for service in the fleet.

For the fleet claimed most of his attention. He saw, as I think, that the approach by sea was easier for the king's army than that by land: he also thought Piraeus more valuable than the upper city; indeed, he was always advising the Athenians, if a day should come when they were hard pressed by land, to go down into Piraeus, and defy the world with their fleet.