History of the Peloponnesian War

The next day the Athenians began building the wall to the north of the Circle, at the same time collecting stone and timber, which they kept laying down towards Trogilus along the shortest line for their works from the great harbour to the sea;

while the Syracusans, guided by their generals, and above all by Hermocrates, instead of risking any more general engagements, determined to build a counterwork in the direction in which the Athenians were going to carry their wall. If this could be completed in time the enemy's lines would be cut; and meanwhile, if he were to attempt to interrupt them by an attack, they would send a part of their forces against him, and would secure the approaches beforehand with their stockade, while the Athenians would have to leave off working with their whole force in order to attend to them.

They accordingly sallied forth and began to build, starting from their city, running a cross wall below the Athenian Circle, cutting down the olives and erecting wooden towers.

As the Athenian fleet had not yet sailed round into the great harbour, the Syracusans still commanded the sea-coast, and the Athenians brought their provisions by land from Thapsus.