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.