In later times works were constructed, and attacks. made on fortresses under the protection of covered ways, or ap proaches. These approaches were generally the work of great expense and labour, being guarded on one side, and sometimes also on the other, with a mound of earth, and covered on the top with skins of animals, rafters, or bun dles of rods, called fascines. At the extremity of the ap proach was erected, as close to the walls as necessary, either an agger, or a moveable tower, according to cir cumstances.
Such were some of the defensive works used by the ancients in carrying on a siege, or in making a sudden attack on a fortified place. Of their offensive weapons, we have already given an ample account under the articles ARMS and ARTILLERY, to which we refer our readers. Of the methods employed by the besieged for destroying, Ind otherwise rendering unserviceable, the machines of the enemy, we have also spoken under the article ARCHI MEDES, where we took occasion to state our opinion with regard to the wonderful power ascribed to the mechanical inventions of that distinguished mathematician. We would only observe farther on the subject of ancient fortification, that mining seems to have been practised at a very early period, and with considerable success, especially in des troying the towers and aggera of the besiegers. The earth under these works being excavated, the place was filled with combustible matter, and set on fire. The super incumbent earth was thus rendered friable, and sinking down, the towers were overturned.
The invention of gunpowder, (anno 13300 though ulti mately destined to produce a revolution in the system of defending and attacking fortified places, was not immedi ately productive of this effect. When great guns began to be first used, they were so rude and unmanageable, that the battering engines of the ancients long maintained their ground. Even so late as the beginning of the 15th cen tury, few towns had been regularly bombarded, though artificial fire works had been frequently used, sometimes in the form of rockets, and sometimes fastened to hinds tails, for the purpose of setting fire to such parts or the town or camp as were of a combustible nature. It was a device of this kind, that proved fatal to the camp of the Austrians before Saaz.
About the beginning of the 16th century, the use of great guns became more common, and their effects began to be more apparent. The circumvallations of the be siegers gradually assumed the form of regular fortifica __ tions ; and fortified places themselves underwent a con siderable change both in form and strength. We cannot here enter into a detail of these changes, without suppos ing our readers to be acquainted with the principles of the art, which it is the object of this article to explain. It may, however, be observed in general, that the use of modern artillery had not of itself the effect of shortening the duration of sieges. The advantages of great guns, especially after men had acquired considerable dexterity in the management of them, were no doubt very great to the besiegers ; but they also afforded to the besieged a powerful means of annoying the enemy. Besides, fortified
places were sometimes so successively strengthened, as for a long time to defy even the force of the heaviest ordnance. A wall at Magdebourg, received 1550 cannon shot without sustaining any damage. The numerous in stances too, which history affords of long and unsuccessful sieges, 'even after the invention of fire arms, prove that this invention was not more advantageous for attacking than for defending fortified places. The siege of an im portant place was almost decisive of the fate of the and if not successful on the part of the besiegers, gene rally terminated in the loss of the greater part of their army.
Such was the state of fortification, when, towards the end of the 17th century, lI. Vauban effected a complete revolution in the art. This celebrated engineer invented a new method of attack, against which no mode of defence hitherto adopted has been able to hold out. Vauban him self indeed soon discovered the superiority of his system of attack to that of his defence, and, during the latter part ofihis life, endeavoured to restore the equilibrium which he had destroyed. His disciples, as well as those who differed in some points from him, continued to labour in the same cause ; but after all the changes and improve ments which they introduced into his plan of defence, it was found, that they had done nothing to counteract the power which had been put into the hands of the besiegers. That power was soon pronounced to be irresistible, and at the same time so regular in its operations, that the dura tion of a siege was calculated as easily, and in many cases as accurately, as a question in dynamics. Such calcula tions applied to the operation of moral causes, may indeed seem very absurd; but so deeply have engineers been im pressed with the idea, that it is utterly impossible to hold out against the modern system of attack, that a siege generally terminates after a certain progress has been made by the besiegers, whatever may be the means of de fence which the garrison still possesses. Such a system appears to be an agreement entered into among belligerent powers, to deliver up to one another fortified places at a certain price, and certainly has a tendency to suppress that fortitude and determined spirit of resistance, which the history of ancient, as well as of some modern sieges, has proved to be the chief cause of a long and successful de fence.
In the remaining part of this article, we shall to lay before our readers a complete account of the modern plan of fortification, with the art of attacking and defend ing fortified places. In this account we shall take an op portunity of noticing the various improvements which have either been proposed or actually adopted ; and among others, the plan of defence recommended by Carnot, who has long been distinguished by mathematical, political, and military talents, and well known for his famous defence of Antwerp, in 1813.