Chapter 3 - The Military Revolution
Siegecraft
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This remarkable innovation in warfare came into existence in an attempt to deal with one of the most powerful defensive systems produced by the Iron Age, the fortified city. By the Bronze Age there was unambiguous evidence of fortifications built exclusively for military purposes. The first undisputed example of a fortified city was Urak in Mesopotamia dating from 2700 B.C. It enclosed a population of 3,000 to 5,000. Within 200 years, fortification of urban areas had become the norm.

The fortifications of the Bronze Age were remarkable for the time. The fortress of Buhen built in the Sudan around 2200 B.C. was 180 yards square, surrounded by a mud-brick wall 15 feet thick and 30 feet high. The wall had firing bastions every 30 feet. A moat surrounded the outer wall and was 26 feet across and 18 feet deep, with yet another steep glacis on the inner slope. The gate complex was 45 feet high and stretched from the inner wall across the moat, allowing archers to control fire along parallel approaches. As impressive as this fortress was, it was dwarfed in size and complexity by fortifications of the Iron Age. The Israelite fortress at Hazor, for example, had walls that ran 1,000 meters by 7,000 meters. The city of Qatna had walls 4 miles long, and the Hittite capital of Boghazkoy had walls that ran for 6 miles. The entire wall of Boghazkoy and its supporting strong points were made of solid rock and brick. So important were fortifications to the ancient armies that the need to secure adequate wood and stone supplies led both Egypt and Assyria to occupy Lebanon for centuries on end.

Fortified cities put field armies at great risk. Safe behind the city's walls, defending armies could provision themselves for long periods, while the attacking armies were forced to live off the land until hunger, thirst, and disease ravaged them. Worse, no army bent on conquest could force a strategic decision as long as the defender refused to give battle. A conquering army that sought to bypass fortified strong points placed itself at risk of surprise attack from the rear at a time of the enemy's choosing. Even in ancient times, the success of a conquering army depended upon its ability to overcome fortified strong points and cities if it was to achieve its strategic and tactical objectives. The ability to overcome fortifications was an art that no successful army could afford to be without.

Not surprisingly, the military engineers of ancient armies invented the techniques of siegecraft, one of the most sophisticated expressions of the military art. One of the earliest inventions to overcome fortifications was the battering ram, which dates from at least 2500 B.C. By 2000 B.C., it was a normal implement of warfare. The ability to secure large spear blades to long beams allowed engineers to pry stones loose from the walls until a breach was achieved. The Hittites used the technique of building an earthen ramp to a low spot in the wall and then rolling large, covered battering rams into place to attack the wall at its thinnest points. The Assyrians built wooden siege towers taller than the defensive walls and used archers to provide cover fire for the battering ram crews working below. The Assyrians also perfected the use of the scaling ladder by using short ladders to mount soldiers with axes and levers who dislodged the stones in the wall at midpoint. Longer ladders were used to insert combat forces over the walls.

The absolute masters of rapid siege assault were the Assyrian armies of the 8th century B.C. The key was to coordinate several different types of assault on the walls at the same time but in different places. Battering rams supported by siege towers were brought into position at several points along the wall. At the same time scaling ladders with lever crews were deployed at other points. Sappers and tunnelers worked to gain entry from beneath by weakening and collapsing a section of the foundation. At the appropriate time, scaling ladders were used to mount attacks over the wall at several points in an effort to force the defender to disperse his forces. The idea was to quickly mass more soldiers at the point of entry than the defender could bring to bear. As a rule of thumb, a city could mount about 25 percent of its population to defend against attack. Thus, a city of 30,000 could muster fewer than 8,000 men to defend against an attacking force that typically exceeded 30-40 thousand soldiers. The advantage almost always rested with the besieging army.

The armies of classical Greece, as in so many other areas of military expertise, were hopelessly primitive in the arts of siegecraft. These armies had no siege trains and relied primarily upon blockade and starvation to subdue a city, techniques far too slow to be used by an army trying to force a strategic decision. In the late classical period these citizen armies made a few rudimentary attempts at using siege engines. In 440 B.C., Artemon used siege towers in the siege of Samos, but failed to take the city. In 424 B.C. the Boetians may have used a primitive flamethrower -- a hollow wooden tube that held a cauldron of burning sulphur, charcoal, and pitch at one end -- against the wooden walls of Delium. In 397 B.C., Dionysisus successfully used siege towers and rudimentary catapults in the attack on Motya.

The steady development of siegecraft resumed once again during the reigns of Philip and Alexander. Philip realized that the new Macedonian army would remain a force fit only for obtaining limited objectives if it was not provided with a capability for rapidly reducing cities. Alexander's far-flung victories would have been impossible without this capability. Philip introduced the use of sophisticated siege operations into his army, copying many of the techniques first used by the Assyrians and passed to him by the Persians. Both Philip's and Alexander's armies made regular use of siege towers, battering rams, fire arrows, and the testudo.

The Roman ability to reduce fortifications was probably the best in the ancient world, but relied on organization and application rather than on engineering innovations. For the most part Roman siege engines were significantly improved versions of the old Greek and Persian machines. Most important, Roman siegecraft depended upon manpower, organization, discipline, and determination more than machinery. Once the Romans were committed to a siege, the results were almost inevitable, no matter how long it took.

The Romans raised the art of circumvallation and countervallation to new heights. At Masada, they built a stone wall around the entire mountain. Manned at regular intervals with soldiers, the purpose of the wall was to prevent anyone from escaping the besieged fortress. When there was a threat of an attack from a relieving army, circumvallation was supplemented by countervallation, in which yet another wall was built so that troops could defend against an attack from a relieving force. These techniques often took a great deal of time. In the case of Masada, the Romans laid siege to the mountaintop fortress for 3 years. In the process they built a 3-mile-long sloping earthen ramp to the top, along which they moved siege machinery and troops for the final assault.

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