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
