into nine stories.  The turris, a tower of the same class, was used both by Greeks and Romans, and even by Asiatics.  Mithridates used one at the siege of Cyzicus one hundred and fifty feet in height.  These most formidable engines were generally made of beams of wood covered on three sides with iron and sometimes with rawhides.  They were higher than the walls and all the other fortifications of a besieged place, and divided into stories pierced with windows; in and upon them were stationed archers and slingers, and in the lower story was a battering-ram.  The soldiers in the turris were also provided with scaling-ladders, sometimes on wheels; so that when the top of the wall was cleared by means of the turris, it might be scaled by means of the ladders.  It was impossible to resist these powerful engines except by burning them, or by undermining the ground upon which they stood, or by overturning them with stones or iron-shod beams hung from a mast on the wall, or by increasing the height of the wall, or by erecting temporary towers on the wall beside them.

Thus there was no ancient fortification capable of withstanding a long siege when the besieged city was short of defenders or provisions.  With forces equal between the combatants an attack was generally a failure, for the defenders had always a great advantage; but when the number of defenders was reduced, or when famine pressed, the skill and courage of the assailants would ultimately triumph.  Some ancient cities made a most obstinate resistance, like Tarentum; like Carthage, which stood a siege of four years; like Numantia in Spain, and like Jerusalem.  When cities were of immense size, population, and resources, like Rome when besieged by Alaric, it was easier to take them by cutting off all ingress and egress, so as to produce famine.  Tyre was taken by Alexander only by cutting off the harbor.  Cyrus could not have taken Babylon by assault, since the walls were of such enormous height, and the ditch was too wide for the use of battering-rams; he resorted to an expedient of which the blinded inhabitants of that doomed city never dreamed, which rendered their impregnable fortifications useless.  Nor probably would the Romans have prevailed against Jerusalem had not famine decimated and weakened its defenders.  Fortified cities, though scarcely ever impregnable, were yet more in use in ancient than modern times, and greatly delayed the operations of advancing armies; and it was probably the fortified camp of the Romans, which protected an army against surprises and other misfortunes, that gave such permanent efficacy to the legions.