Fortification and Siege Warfare

I

Introduction

Fortification and Siege Warfare, related branches of the art of military engineering. Fortification deals with the design and construction of defensive structures; siege warfare involves systematic efforts to attack and capture such structures.

II

Temporary and Fixed Positions

Defence works may be permanent or temporary. Examples of the former are city walls, the castles of the Middle Ages, and the frontier fortresses and harbour defences of relatively modern times. The construction of permanent defensive works implies a continuing requirement for the protection of political, economic, or military interests associated with a particular locality; the development of temporary or field fortification is associated with tactical requirements in the field (see Tactics). Examples include the palisaded camps built by the Roman legions for overnight halts, the pointed wooden stakes used by English foot soldiers to throw enemy cavalry into confusion under arrow fire, and the use of trenches and sandbags in more modern warfare. When a moving situation becomes stabilized, a hastily occupied defensive position may have to be developed into a more strongly fortified position; the classic example of such a development is the stabilization of the western front in Europe during World War I, when trenches and other temporary defence works became permanent fortifications.

III

Construction of Fortifications

The primary aim in fortifying a fixed position is to erect a physical barrier that cannot be suddenly overrun and that is strong enough to enable the defending force to hold the position for a period of time. In African village warfare, a thick thorn hedge might serve this purpose, especially if it were green enough not to catch fire. On the frontier of the United States, a stockade of logs firmly set in the earth and loopholed for musketry proved a most useful type of fortification. Over the ages and in most locales, however, the classic defensive barrier has been a masonry wall surrounding the area to be defended, and was usually surrounded by a deep ditch.

The attack on and defence of masonry structures—whether city walls, isolated forts and castles, or extensive barriers such as the Median Wall between the Tigris and Euphrates rivers in Mesopotamia, the Great Wall of China, or the variety of frontier walls built by the Romans against barbarian attack—involved three basic concepts that remained unaltered until the age of gunpowder. In order to reach the defenders, the attackers had to scale the wall, break a passage through it, or burrow underneath it. The techniques of siege warfare were directed towards the accomplishment of these aims, singly or simultaneously, and the techniques of fortification were aimed at preventing such accomplishment.

These opposing techniques interacted, with fortifiers seeking to build the impregnable fortress while besiegers strove to develop the irresistible siege; the effectiveness with which these aims were pursued varied widely through history. Natural defensive strength was the criterion for selection of city sites. In Greece, for example, the huge rock of the Acropolis was the location of the earliest Athenian settlers; the Seven Hills of Rome amid the marshes of the Tiber River provided a strong defensive situation for that city. The Phoenicians of the ancient city of Tyre, finding their coastal position too exposed to marauders, moved to an offshore island and added a water barrier to their defences. The art of fortification developed through local necessities and, as the wealth and power of the cities grew, often became undermined by complacency. The art of attack by siege, on the other hand, was stimulated by the efforts of those who would be conquerors.

IV

Siege Techniques

In former times, setting siege to an enemy stronghold demanded enormous labour. Movable wooden towers, or belfroi, were built, from which bows and arrows or slings could be aimed at the garrison, and from which the top of the enemy wall could be attacked. Such towers were of enormous weight; one used at the siege of Rhodes by Demetrius I, king of Macedonia, in 305 bc required 3,400 warriors to move it. Soldiers in the lower stories of the tower attacked the wall with battering rams (see Battering Ram), consisting of tree trunks swung by ropes from overhead beams, with rounded metal heads to crumble the masonry, or with borers, which were similar devices with axe-shaped heads to attack crevices and to wrench stones out of the face of the wall. The defenders, in turn, would normally attack the wooden tower with fire, against which raw animal hides were the usual method of protection.

Missile-throwing engines included the catapult, which, in principle, was a giant spear-throwing crossbow attached to a timber stand, and the ballista, which used the torsion of heavy cords twisted between two uprights to throw stones weighing up to 45 kg (up to 100 lb) each, although with little accuracy.