The Physics of War (3 page)

Tiglath-pileser III began by introducing dramatic changes. First he increased the efficiency of the Assyrian administration. Then he turned his attention to the army, which had become significantly weakened over the years.
At this time the only army that existed was quite small; when a large army was needed, recruiters were sent out to round up farmers and anyone else they could get, and the conscripts were usually given very little training. Tiglath-pileser set up a large standing army, one of the first in history. And the soldiers were given uniforms and some of the best weapons of the time. He also significantly improved the roads throughout Assyria.

An Assyrian warrior.

Chariots were still being used, but Tiglath-pileser immediately saw the advantage of cavalry, setting up a large cavalry division. The Assyrians did not have much experience with horses, and they were initially not nearly as good on them as the barbarians were. But with training they improved. At first the Assyrian cavalrymen worked in pairs, with one controlling the horses and the other shooting arrows. But soon each warrior had his own lance and control of his own horse. Cavalry eventually became the core of the Assyrian army, with thousands of cavalrymen on horses. This meant, of course, that large numbers of horses were needed, and Tiglath-pileser also took care of this. Large stables were set up to raise and care for horses.

There's no doubt that the Assyrians were a “warring nation” right from the beginning. They were, in fact, at war most of the time they were in power. And under Tiglath-pileser they continued their warring ways, conquering country after country. Not only did Tiglath-pileser build up the cavalry; he also significantly improved the infantry. The infantry consisted of archers, shield bearers, slingers, and spearmen. Slingers, who threw stones, were frequently used to distract the enemy. Large shields were used by most nations to protect their forces against the onslaught of arrows. Arrows were usually fired high so they would drop down on the enemy; the shield bearers would therefore hold their shields over their heads to protect the infantry. Tiglath-pileser employed slingers to project stones directly at the enemy, and to protect themselves they had to lower their shields. The Assyrian archers would then fire over their heads so that falling arrows would not be deflected by their shields. Tiglath-pileser also introduced lancers; they were soldiers with particularly long spears, called lances. They were much longer than swords are daggers, and, as a result, when they were used in an attack, swords were quite ineffective against them.
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There was, however, a serious problem for the Assyrians. So many nations were at war at this time that cities and towns were in constant danger of being invaded, not only by other nations, but even by their neighbors. And they needed protection. Kings and rulers, with their huge egos and aggressive ways, were always hungrily eyeing the resources and wealth of their neighbors and neighboring countries. Few were satisfied with what they had. War was a natural thing, and they had to go to war not only to conquer new lands, but also to build up their treasury.

The Assyrians were certainly guilty of this. Furthermore, it was well-known to all their enemies in the surrounding countries that they were brutal. They frequently killed entire populations, and they killed indiscriminately. They also used mass deportation as a terror weapon. If there were uprisings in any of the countries they conquered, they would deport thousands of people to other lands.
Tiglath-pileser was well known for this. For example, in 744 BCE he deported sixty-five thousand people from Iran to the Assyrian-Babylonian border, and in 742 BCE he deported thirty thousand people from Syria to the Zagros Mountains in present-day Iran.

Because of these practices, many people put considerable effort into building huge walls around their towns or cities for protection. These walls were usually several feet thick and at least twenty feet high. Several years were frequently spent building them. The earliest walls were made of mud mixed with various other materials; they were thick enough to give some protection, but it soon became obvious that they were vulnerable. Mud was not very strong. Nevertheless, an enemy would frequently bypass a city if its walls were too thick and high. It was usually too much trouble for them.

Walls, however, were merely a challenge to the Assyrians. They weren't going to let walls stop them, and they soon began designing and building siege engines to get through them. Actually, they were nothing more than huge battering rams constructed of wood. In many ways they resembled a gigantic tank on wheels. They usually had four wheels, but some of the later ones had six. And because they were so big and heavy, it usually took thousands of soldiers to move them.

As terrifying as they were, the defenders usually fought back with all they had. The siege engines would have to be pushed up to the edge of the wall, and it soon became obvious that the pushers and anyone inside would need protection while it was being moved forward, since the defenders would bombard them with arrows and rocks, and as the siege engine moved close to the wall they would try to set it on fire. For protection, the Assyrians built small towers atop their siege engines for their archers. These archers would fire back at the defenders as the siege engine was being moved forward.

When the siege tower, which was frequently several stories high, reached the wall, a huge battering ram with an iron (or bronze) “bit” was rammed again and again against the wall. It was powered by a large contingent of soldiers. Slowly it would chip away at the wall, and as this took place, fierce fighting would go on between the Assyrians and the defenders. Fire, of course, was a major weapon of the defenders, so the Assyrians had to cover their engine with a huge sheet of animal skins that was kept wet.

As time passed, walls were built thicker and thicker, and eventually stone walls were used. But the Assyrians merely built bigger and bigger siege engines with more effective metal bits. As stone increasingly came to be used for the construction of city walls, it became more and more difficult for the siege engines to batter them down. Nonetheless, they continued to have some success. One of the
largest siege engine of ancient times was the Greek
helepolis
; over one hundred feet high and so stable it could not be tipped over, it far outstripped the scale of Assyrian siege weapons.

Over time, the Assyrian Empire began to weaken. It had collapsed by about 610 BCE.

GREEKS AND THE BEGINNING OF PHYSICS

While the Assyrian Empire began to fade, other nations began to flourish, including Babylonia, the Persian Empire, which lasted to 330 BCE, and Phoenicia, the seafaring state that lasted to about 539 BCE. But the ancient civilization that had the biggest influence on physics was Greece, which consisted of city-states that began coming into power about 800 BCE. Indeed, before the Greeks, there was little if anything that could be called physics, and there was little science in general. Furthermore, the first scientists were not referred to as such; they were referred to as philosophers. But there's no doubt that one of their major aims was to understand the world around them. They were particularly interested in motion and matter. Why did things fall? And what exactly was the role of air, water, fire, and the earth beneath their feet? What was time? And their curiosity extended to the sun, the moon, and the stars. How far away were they? How big were they? Why did they seem to move?

The first science was, no doubt, a form of physics. It was not what we think of as physics today, but it did include many of the same topics. It was drawn from astronomy, mechanics, optics, and areas of mathematics such as geometry. The early Greek philosophers set out to understand the mysteries of the earth and the known universe, and although they arrived at some ideas that may seem strange to us today, they did make important advances. One of the biggest advances was to move away from mythological explanations for the phenomena they observed. Instead, they developed logic and learned to look for reasonable and logical explanations.

One of the first of these philosophers was Thales, who lived from 624 to 546 BCE. He was the first to emphasize the importance of explanations based on reason, and he was particularly interested in why things happened. Because of his contributions he is sometimes referred to as the father of science. He is said to have predicted the eclipse of May 28, 585 BCE. There is some controversy about this, however, as most modern astronomers feel that such a prediction was not possible at that time. But there is no controversy about his most important contribution. At that time Greek sailors never left the sight of land because they
had no idea how to navigate when no land was visible. Thales showed them how to use Polaris (the North Star) for navigation. He also studied the strange phenomena associated with magnetism and amber, and he took a serious interest in the phenomena of time and the basic nature of matter.

The two major philosophers who came after Thales, namely Socrates and Plato, were both giants of rational thought, but their interest was mostly in logic, philosophy, and mathematics. Socrates was considered one of the wisest people of his time, but science was not central to his thinking. Plato, a student of Socrates, was probably most famous for his founding of the Academy of Athens.

In 384 BCE, however, the ancient philosopher best known to us was born: Aristotle. He was highly influential in his own era, and he remains influential today. He was strongly interested in science, and he made several contributions, but because his influence has extended over such a long period of time, he is frequently regarded as someone who hindered the development of science. Nevertheless, his goals were admirable. As he stated in his writings, his main aim was to discover principles and causes of change, and not just describe them. Much of what he came up with, however, was erroneous. One of his major hypotheses was that there were four basic elements: earth, water, air, and fire. And he postulated that everything was made up in some way from these four elements. He also had a strong interest in the phenomena of motion, and he classified all motions as either “natural” or “violent.” A falling object had natural motion; a thrown object had violent motion. He also believed that everything beyond the earth—sun, moon, and stars—was made up of a fifth element he called “ether.”
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A number of other Greek scientists of the time also made important contributions. Eratosthenes (276–194 BCE) invented a system of latitude and longitude for the earth. He also calculated the circumference of the earth using the shadows of sticks at different positions. In particular he pointed out that if the earth was flat, there should not be shadows from vertical sticks at different positions at the same time (only one could be shadowless) when the sun was directly overhead. He used his new knowledge to calculate the circumference of the earth to be two hundred fifty thousand stadia (we're still not sure however what a stade is). He also calculated the distances of the sun and the moon, giving us first, but very approximate, estimates.

Another important early Greek scientist was Hipparchus, who was born in 175 BCE. He gave us more accurate measurements of the distances to the sun and to the moon, and he was the first to set up a catalog of most of the visible stars.

Physics first appeared as a result of the studies and speculations of the above philosophers. It's important to note, however, that their contributions
came almost entirely from “thought.” Experimental physics was not known at the time, and, indeed, the early philosophers did not perform any experiments in their attempts to prove their ideas. Nevertheless, even at that time they realized that there was a difference between what we call “pure physics” and “applied physics.” Pure physics is usually thought of as the accumulation of knowledge about the physical aspects of the world and universe, such as the basic principles of space, time, matter, motion, and so on, with no thought of how this knowledge should be applied. Applied physics, on the other hand, is the application of this knowledge to assist society in some way. At that time, the main application of physics was the design and manufacture of war machines. Early philosophers such as Socrates, Plato, and Aristotle argued that science should not necessarily have applied goals, particularly applications to war. Knowledge should be accumulated for its own sake.

In spite of the arguments against doing so, it wasn't long before the new discoveries of physics were being used to build new weapons of war. Many of the early advanced weapons built by the Greeks were based on an important physics concept called torsion. In physics, torsion is the twisting of an object due to an applied torque, where torque is a twisting force. And indeed, torsion soon became the basis of new terror weapons that were frequently referred to as machines or engines.

THE NEW WONDER MACHINES

The most common new wonder machines that came out of Greek physics (though not necessarily constructed by the Greeks) were the ballista, the onager, the trebuchet, and various other types of catapults. We talked about siege machines earlier that were used to break through walls; some of the above were also eventually used as siege machines. Let's look at each of them in turn. The ballista was invented by the Greeks and later modified and used extensively by the Romans. It was similar to a giant crossbow, but it used torsional energy that was stored in twisted skeins. Two wooden arms were used to twist the skeins; ropes were attached to one end of each of them, with the ropes extending back to a “pocket” that held the projectile. The ropes were pulled back by a winch. It had a trigger on it, and when everything was ready to go, the trigger was pulled. Various types of projectiles were used, including stones, darts, shaped poles, and even body parts. It could throw them several hundred yards.
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