Military engineers invented the techniques for overcoming the defenses of fortified cities. One of the earliest inventions was the battering ram, which dates from at least 2500 b. c. e. 15 By 2000 b. c. e. the battering ram was found in almost all armies of the ancient world. The Egyptians also invented the technique of securing a large metal blade to a heavy pole and using it to pry bricks and stones from the walls to create a breach. The Hittites used the technique of building an earthen ramp to a low spot in the wall and then rolling large covered battering rams up to the wall to attack it at its thinnest point. Assyrians and Persians constructed massive siege towers that were taller than the defensive walls, using archers to provide cover fire for the battering ram crews working below. Persian siege towers were set on wheels and moved with the army. The scaling ladder was one of the earliest siegecraft devices. Egyptian texts tell of soldiers strapping their shields on their backs to have both hands free to climb the ladders. The shields acted like a turtle’s shell, protecting the soldiers from stones and arrows thrown down on them by the defenders. The Assyrians sometimes used a short scaling ladder to mount soldiers with axes and levers to dislodge stones mid-way up the wall, while tunnelers weakened it from below. Longer ladders were used by all armies to insert combat forces over the walls.
If an army was to preserve the offensive, it had to subdue fortifications quickly. The absolute masters of rapid assault on cities were the Assyrian armies of the seventh century b. c. e. The key to success was to coordinate several different types of assaults on the walls at the same time but at different points. Battering rams supported by siege towers were first brought into position at several points along the wall. Scaling ladders with lever crews were deployed at other points. Sappers and tunnelers worked to gain entry from beneath the wall by weakening and collapsing a section of the foundation. (This worked very well if the walls were casement walls. Casement walls are really two walls filled with rubble between them. By weakening the outer wall, the weight of the rubble itself pressing out against the weakened wall would cause the wall to collapse.) At the appropriate time, long scaling ladders were used to mount attacks over the walls at several points to force the defender to disperse his forces.
The armies of Classical Greece were hopelessly primitive in the art of siegecraft, as were the tribal armies of Gaul and Germany. Carthaginian armies also lacked siege trains. After the battle of Cannae, Hannibal failed to attack Rome largely because he lacked the siege equipment to do so. Greek armies relied primarily on blockade and starvation to subdue a city, methods far too slow to be used by an army trying to force a strategic decision. It was not until the late Classical period that the citizen armies of Greece made a few rudimentary attempts at using siege engines. In 440 b. c. e. Artmon used siege towers against Samos but failed to take the city. In 424 b. c. e. the Boetians may have used a primitive flamethrower-a hollow wooden tube that held a cauldron of burning sulfur, charcoal, and pitch at one end-against the wooden walls of Delium. In 397 b. c. e. Dionysisus successfully employed siege towers and rudimentary catapults in the attack on Motya.
Greek armies did not begin to approach the siegecraft capabilities of the armies of the Near East until the reigns of Philip of Macedon 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 the capability for rapidly reducing cities. Alexander’s victories would have been impossible without this capability. Philip introduced sophisticated siegecraft capabilities into his army, copying many of the techniques 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, fi re arrows, and the testudo (a device wheeled up to the wall of the fortified city that protected the attackers against the defenders).
Alexander’s campaigns against the Indian republics after the battle of the Hydaspes River (326 b. c. e.) provide a glimpse into the nature of Indian fortifications and Alexander’s methods of reducing them. Curtius tells us that although most Indian towns had walls, probably erected to protect against bandits, most did not have proper fortifications and were easy targets. Others were more difficult because they took advantage of terrain characteristics, such as building on a hill or steep cliff. Important towns, however, displayed impressive fortifications. Curtius described Massage as being defended by
an army of 38,000 infantry . . . a city that was strongly fortified by both nature and art. For, on the east an impetuous mountain stream with steep banks on both sides barred approach to the city, while to the south and west nature, as if designing to form a rampart, had piled up gigantic rocks, at the base of which lay sloughs and yawning chasms hollowed in the course of ages to vast depths, while a ditch of mighty labor drawn from their extremity continued the line of defense. The city was surrounded by a wall 35 stadia [6.2 kilometers] in circumference which had a basis of stonework supporting a superstructure of unburnt, sun-dried bricks. The brickwork was bound into a solid fabric by means of stones… Strong beams had been laid upon these supporting wooden floors which covered the walls and afforded passage among them.
To overcome these defenses, Alexander had his troops demolish the houses outside the walls to make a platform. Depressions in the ground were filled in with stones and trees to make a level platform. On the leveled ground Alexander had his men construct several mobile wooden siege towers and placed his ballistae on their tops. The ballistae then hurled stones down on the defenders, shattering their walls. Curtius says that the defenders were awed by the ballistae, implying that they might have been unknown in India at this time. The texts describing Indian siege techniques do not describe ballistae and focus mostly on defensive measures, such as fi repots thrown from the walls or satghanis, a large wooden log with metal spikes that could be dropped from the walls to crush attackers below. Another weapon, the yantra, may refer to a device for hurling stones and missiles at the enemy, but we have no information as to its design. We might reasonably conclude that both fortifications and the techniques for demolishing them were not as highly developed in India as they were in the Near East, at least during Alexander’s time.
Military fortification seems to have come late to China, at least on any large scale. It is only with the dawn of the Warring States period (464-221 b. c. e.) that we begin to find the regular fortification of cities and towns for military purposes. Chinese military architecture, including the Great Wall, is credited with a major innovation in construction. By mixing mortar with rice milk instead of water Chinese engineers invented a new kind of mortar that was relatively impervious to rain and moisture. Its strength, when dry, also permitted the laying of bricks at very steep angles without having the structural load of the bricks pull the structure apart. The introduction of extensive fortifications led to developments in siegecraft, including the use of specialized equipment, such as chariots with large shields to protect workers, wheeled towers and rams, movable ladders, catapults, and powerful crossbows that could discharge several large bolts at once. On campaign it was customary for armies to construct fortified camps with walls of rammed earth.
The Roman ability to reduce fortifications was probably the best in the ancient world, but it relied primarily on organization and application rather than on engineering innovation. Roman siege engines were mostly improved versions of the old Greek and Persian machines. The Romans used armored siege towers, some as high as twenty-four meters; massive iron battering rams far larger and heavier than any predecessor; large iron hooks to dislodge stones; covered platforms to protect miners and assault teams; and bridges, drawbridges, and elevators mounted on towers to swing assault teams over the walls. Most important, Roman siegecraft depended on manpower, organization, discipline, and determination. Once the Romans were committed to a siege, the results were inevitable, no matter how long it took to succeed.
The Romans raised the art of circumvallation and countervallation to new heights. At Masada they constructed 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 from a relieving army, circumvallation was supplemented by countervallation, where another wall was built so that the troops could defend against an attack from a relieving force. Caesar did this at the siege of Alesia in 52 b. c. e. Constructing these walls took considerable time. In the case of Masada the Romans laid siege to the mountaintop fortress for three years. In the process they constructed a three-mile-long sloping earthen ramp to the top, along which they moved siege machinery and troops for the final assault.
It was Philip of Macedon who first organized a special group of engineers within his army to design and build catapults. Philip’s and, later, Alexander’s use of catapults allowed Greek science and engineering to contribute to the art of war. By the time of Demetrios I (305 b. c. e.), known to history as Poliorcetes (“the Besieger”), Greek inventiveness in military engineering was probably the best in the ancient world. It fell to Alexander’s engineers to develop a number of new ideas. Diades invented a hook mounted on a lever suspended from a high vertical frame that was used to knock down the upper parapets of a wall. Diades also invented the telenon, a large box that could hold a number of armed men. Suspended from a tall mast, the telenon could be raised and lowered on tackle like an elevator to hoist men over the walls. To this day, the military art of siege warfare is called “poliocretics,” in honor of the Greek contributions to the art.