The usual mode of assailing fortified towns in the time of the Peloponnesian war, was to build a double wall round them, sufficiently strong to check any sally of the garrison from within, or any attack of a relieving force from without. The interval within the two walls of the circumvallation was roofed over, and formed barracks, in which the besiegers posted themselves, and awaited the effects of want or treachery among the besieged in producing a surrender. And, in every Greek city of those days, as in every Italian republic of the middle ages, the rage of domestic sedition between aristocrats and democrats ran high. Rancorous refugees swarmed in the camp of every invading enemy; and every blockaded city was sure to contain within its walls a body of intriguing malcontents, who were eager to purchase a party-triumph at the expense of a national disaster. Famine and faction were the allies on whom besiegers relied. The generals of that time trusted to the operation of these sure confederates as soon as they could establish a complete blockade. They rarely ventured on the attempt to storm any fortified post. For the military engines of antiquity were feeble in breaching masonry, before the improvements which the first Dionysius effected in the mechanics of destruction; and the lives of spearmen the boldest and most highly-trained would, of course, have been idly spent in charges against unshattered walls. A city built, close to the sea, like Syracuse, was impregnable, save by the combined operations of a superior hostile fleet and a superior hostile army. And Syracuse, from her size, her population, and her military and naval resources, not unnaturally thought herself secure from finding in another Greek city a foe capable of sending a sufficient armament to menace her with capture and subjection. But in the spring of 414 B.C. the Athenian navy was mistress of her harbour and the adjacent seas; an Athenian army had defeated her troops, and cooped them within the town; and from bay to bay a blockading wall was being rapidly carried across the strips of level ground and the high ridge outside the city (then termed Epipolae), which, if completed, would have cut the Syracusans off from all succour from the interior of Sicily, and have left them at the mercy of the Athenian generals. The besiegers' works were, indeed, unfinished; but every day the unfortified interval in their lines grew narrower, and with it diminished all apparent hope of safety for the beleaguered town.