It is impossible to say at what time, or in what coun try, men first began to construct fortifications. In a rude state of society, when weapons of attack were few and simple, and when the success of war depended more on the physical powers, than the skill of the combatants, little ingenuity would be necessary to render a place im pregnable, whatever might be the force of the assailants. An earthen mound, a deep ditch, or a single stone wall, would probably be sufficient not only for protecting a garrison against sudden attacks, but even for enabling it to hold out against a regular siege. How long the art of fortification continued in this simple state, we have no means of ascertaining ; but it is evident, from various passages of sacred history, that it had made considerable progress in Eastern countries in the clays of Moses, up wards of 1500 years before Christ. From these countries, it probably travelled to the West, where it received great improvements from the Greeks and Romans. By invent ing new methods of attack, these warlike states obliged the besieged to adopt new methods of defence; and thus while they exercised their own ingenuity in the art of war, they called forth that of the nations with whom they contended. A single mound, or stone wall, was soon found to be altogether inadequate to resist the force of the en gines with which they were assailed. The wall or rampart was accordingly strengthened by towers erected upon it at convenient distances, and from these the besieged were enabled to defend the intermediate parts of the wall, which they could not otherwise have done without exposing themselves to the missile weapons of the enemy. Besides these towers, the rampart itself sometimes consisted of a double or even a triple wall. Of this kind were the walls of Jerusalem and Babylon.
The most obvious method of assaulting a fortified place in rude ages, would be to construct an earthen mound or counter fortification, from which the assailants could en gage with the besieged on equal terms. This method of attack was probably coeval with the art of fortification itself, as from the passages of sacred history to which we have already alluded, it appears to have been common in Eastern countries at the time of the Israelites taking pos session of the land of Canaan. The same method of be sieging towns was adopted by the Greeks and Romans. They constructed their circumvallation of turf, and, in some cases, they were made double at an interval of fifteen or sixteen feet. The interior wall was intended to preserve them from the sallies of the besieged, the exterior to guard them against the attacks of those who might come to the assistance of the town. The space between the walls or mounds was occupied with tents and lodges for the sol diers. These walls were surmounted with turrets, after every tenth of which was a tower, extending from wall to wall, and equal in height to the fortifications of the town. After all, this method of attacking a place was better cal culated to starve it into a surrender, than to take it by force.
Another, and perhaps a more expeditious method of attack, was by means of detached mounds, or aggera, erected opposite the weakest part of the fortification. These aggera were constructed of all sorts of materials, as wood, stone, earth, &c. and gradually carried forward till almost close to the walls. The besiegers were thus raised to a level with their enemies, and sometimes suc ceeded in throwing bridges between the aggera and the fortification, by which they stormed the place. Still, how ever, this method of attack was liable to a serious objec tion. The laborious nature of the operations necessary in constructing even single and detached mounds, or aggera, afforded the besieged time enough to strengthen such parts of their rampart as were threatened, and thus de privenhe assailants of no inconsiderable part of the ad vantage to be derived from their works. The invention of moveable towers or turrets was therefore a very great improvement in the art of attacking. 'These towers were erected on wheels and rollers, by which they could easily be moved from one plaee,to another ; and, in point of size, were proportioned to the height and strength of the place to be attacked. In their most improved form, they con sisted of wood, and were so constructed as to be taken down and carried about with the army as part of the bag gage.
But the great difficulty of attacking fortified places in ancient times, did not consist in the prodigious labour, so much as in the danger to which the besiegers were ex posed in constructing their outworks. From their situa tion, the besieged were enabled powerfully to annoy their enemies, with comparatively little danger to themselves. Huge stones, and other heavy bodies, thrown from the ramparts, became formidable and destructive weapons, against which the besiegers could find no protection in the ordinary means of defence. It was to prevent the fatal effects of such weapons, that the tcstudo was in vented. This consisted of a number of soldiers, arranged in different forms according to circumstances, but all hold ing their shields above their heads, thus forming a canopy or covering over those who were employed in the works beneath. The testudo was also sometimes employed, for the purpose of taking a place by storm, when the garrison was not in a proper condition to defend itself. In this case, the front rank stood upright, holding their shields before them ; the second held their shields above the heads of the first, at the same time stooping a little ; the third stooped still more, holding their shields also above their hands ; and so on to the rear rank, which was in a kneeling pos ture, thus exhibiting the appearance of a tiled roof. On this roof, another body of men was drawn up in the same form, and protecting themselves in a similar manner. A number of successive stories being thus constructed, those That formed the highest were enabled to engage on equal terms with the besieged, and frequently succeeded in get ting possession of the place.