The Physics of War (6 page)

The third of these catapults, called the onager, was similar to the ballista in
that it also used torsional pressure generated by twisted-sinew ropes. It consisted of a large frame on the ground with a vertical frame attached to it. A spoke, or arm, was attached to an axle that ran through the vertical frame. A bowl-shaped bucket was placed at the end of this arm, with the projectile placed in this bucket. The machine was loaded by pushing the arm back against the tension created by the twisted skeins. When the trigger was released, the arm would swing upward in an arc, releasing a projectile at the top of the swing. As in the case of the other devices, large stones were usually used as projectiles. Onagers usually had a range of about twelve hundred feet.

The Roman Empire was one of the largest military powers the world had ever seen, and it dominated the Western world for over a thousand years. The Roman march to world dominance began with the Punic Wars, the first of which started into 264 BCE. These wars were fought between Rome and the other significant power in the Mediterranean, the Carthaginians. The first of the wars was fought largely at sea, and after a long struggle, the Romans persevered. In the Second Punic War (218 BCE to 201 BCE), however, the Romans came up against Hannibal, the great Carthaginian general, and he overcame them in battle after battle. Hannibal was successful mainly because he outsmarted the Romans. Confident in their ability to win, the Romans were easily led into traps, and over the next seventeen years over a hundred thousand Roman soldiers were killed as a result, but finally the Roman generals began to learn, and eventually they overcame Hannibal.

THE ROMANS AND THEIR WEAPONS

After defeating Carthage, the Romans continued their campaign, eventually conquering most of the area around the Mediterranean, Greece, much of the Middle East, Germany, North Africa, and England. Indeed, they conquered a large portion of the civilized world at the time, and in the process became the greatest military power the world had ever known. And they did it using the best weapons and tactics known at the time. They used body armor consisting of many plates of material layered on others. Most of their armor and weapons were made of either bronze or iron. They did not discover steel. They used a relatively short, but effective sword called a gladius, which was used primarily for thrusting. In addition, the Romans used bows and arrows, javelins, spears,
and a shield called a scutum that was about forty inches tall, thirty inches wide, and slightly curved.

In sieges they used the ballista, the onager, and various other catapults that incorporated springs of various types. Their standard tactic when facing an enemy was to advance with their shields side by side so that they were less vulnerable to enemy fire. The front line, however, was rotated every fifteen minutes to keep it fresh. The soldiers underwent harsh and grueling training, and discipline was strictly enforced.

Although they used the ballista, the onager, and other weapons that were used by the Greeks, they did not try to improve on them. In fact, the Romans made almost no military advances in weaponry. When they noticed that an enemy had something innovative and new, however, they quickly adopted it. Indeed, they appeared to have no interest in science, either in its own right or as something that might be used to develop new weapons. For the most part, they had a disdain for science. When they conquered Greece and Alexandria, hundreds of thousands of scientific texts came into their hands, but they never went to the trouble of translating any of them, and they never made use of anything that was in them. Their view was that they had all they needed to win wars.
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Surprisingly, though, despite their disdain for science, they did excel in engineering. Over the hundreds of years they were in power, they built thousands of miles of roads—some of the best ever seen in Europe. Furthermore, they built a large number of dams along with networks of aqueducts to distribute the water throughout the land. And they built some of the largest and most magnificent buildings seen up to that time. Many of them were based on the arch. They were also excellent bridge builders. So, while they knew little about physics and cared less about it, they actually used many of the basic principles of physics. For their engineering feats they had to understand such concepts as force, weight, stress and strain, and water pressure.
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Roman civilization lasted from about 753 BCE to about 476 CE. It was at its peak in about 250 CE, when it had conquered most of the known civilized world. But its large size eventually caused things to unravel. It was difficult for Rome to oversee so many distant lands and people. In addition, there was strife at home: there were power struggles among the generals, and as a result, several civil wars eventually broke out. After Caesar was assassinated, Octavius and Mark Antony fought a civil war against the assassins, but eventually the two men began to fight each other. Furthermore, because of the extent of their large empire, they began incorporating troops from their conquered lands into their army, along with mercenary troops, until finally these troops came to represent a large fraction of the Roman force. This created a significant change in the army;
no longer did soldiers undergo rigorous training and discipline, and their dedication to Rome decreased significantly.

The only enemies they had, however, were at the boundaries of their empire, and these enemies were barbarians who knew nothing about organized warfare, siege engines, and body armor. And to Rome they were not a significant threat.

But while the Roman army was declining, the barbarians were looking for something that would give them an advantage. And as we saw earlier, the answer was the use of warriors on horses. Most barbarians learned to ride early. The biggest problem was staying on the horse during a fight—in particular, controlling the horse while shooting arrows and using swords along with lances and spears. The first breakthrough was the development of the saddle; the first simple saddle was devised by the Scythians of Eastern Europe. It was a crude affair with horsehair used as cushions in front of and behind the rider. Cloth loops were soon added to it for the rider's feet. Later, a harness was added to give the rider much better control of his horse. Finally, the cloth loops were replaced with iron stirrups, which were particularly helpful in stabilizing a warrior during battle. There is, however, some controversy as to whether the stirrup was used before 376 CE.

The battle of Adrianople, as it was referred to, had its beginnings in 376 CE. One of the barbarian tribes, the Goths of modern-day Turkey, sent a message to the Roman Empire asking if they could occupy some of the conquered Roman land near the Danube River. Thinking they would be good soldiers, the Roman generals allowed them to occupy it. But it turned out to be a mistake. Fighting soon broke out between the Goths and the Romans in the area. Over the next few years, in fact, there were several battles.
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The Roman emperor, Valens, became annoyed and wanted to end the problem once and for all. In 378 he decided to go to Adrianople himself. Leading an army of about thirty thousand troops, Valens arrived in the area of Adrianople in early August. He was informed that an army of about ten thousand Goths, led by the chieftain Fritigern, was marching toward Adrianople and was about twenty miles away. Valens continued on to Adrianople and set up a fortified camp, ready for Fritigern and his army. He was informed that more reinforcements were coming to help him, but he didn't want to wait for them despite strong urging from his generals. He was sure the strong Roman army would easily overcome the barbarians.

Fritigern sent a message to Valens proposing a peace and an alliance in exchange for some Roman territory. Valens was so sure of victory that he rejected the proposal and prepared to charge. As it turned out, Fritigern was just stalling for time; he was waiting for five thousand more highly trained cavalrymen.
To further delay the attack, Fritigern sent troops to set fire to the fields between the armies, and he also tried to initiate negotiations for the exchange of hostages. This did delay the attack, but it also annoyed Valens.

Suddenly a detachment of overanxious Romans began the attack without orders, but they were easy easily pushed back by Fritigern's men. By then, however, it was too late to stop things; the other contingents of Romans continued the attack and broke through the Goth's circle of wagons. At this moment, however, the five thousand highly trained cavalrymen arrived from all directions and encircled the Romans. The cavalrymen were mounted on large, strong horses, and they had developed an extremely effective lance. The weight of the horse behind the lance made for a lethal combination, and the Roman shields were of little help. The Romans also had cavalry, but it was no match for the Goth cavalry. Many Roman cavalrymen deserted.

The Roman troops were soon in disarray. Over the next few hours the Goths slaughtered them. It was one of the greatest defeats the Roman army had ever experienced, and it was a devastating blow to the Roman Empire. The core of the army in the eastern section of the empire was destroyed. The biggest shock, however, was that the Romans were no longer invincible.

Furthermore, many of the important generals of the Roman army were killed. Valens's fate is not known, but according to one story he escaped the battlefield with some bodyguards and hid in a peasant's cottage. Fritigern's men attacked the cottage, and Valens's men tried to defend it by firing arrows at them. But the Goths set fire to the cottage and Valens perished in the flames.

This battle is generally considered the start of the final collapse of Rome, and there's no doubt that it had a serious effect. It showed that the Romans were not invincible. Nevertheless, the empire lasted for another hundred years. During this time, however, it continued to shrink in size. Most of the attacks during the late years of the empire were mounted by another barbarian tribe, the Huns. But they used the same tactics as the Goths.

EARLY ENGLISH-FRENCH WARS

After the fall of Rome in 476, the West entered a period now referred to as the Dark Ages. Few advances in science were made during this time. In addition, relatively few historical and other written records were left during this period, compared to earlier and later periods. The Dark Ages lasted from 476 to about 1500 CE. During this time barbarian tribes—the Mongols, Huns, Goths, and even Vikings from the north—swept across Europe. Physics, and science in
general, was virtually at a standstill for years, but one science did flourish, namely metallurgy. Mounted warriors were now the norm, and they were soon armored. Cavalrymen eventually had a full suit of armor made from small metal rings overlapping one another, referred to as chain. Later, because archers frequently shot the horses out from under them, horses were also armored. As a result, there was a continuing search for metals that would give better protection. And soon after cavalrymen found that arrows were penetrating their chain armor, steel plating was developed.

For many years the armored knight on a horse with a long lance or sword was in the lead when a charge was made. Not only were such mounted knights very effective, but they also had considerable shock value. Few infantrymen would stand their ground against a knight on a horse as it barreled down on them. Furthermore, the speed of the horse was much greater than the speed of a man on foot, so the infantrymen had no place to go. This, along with the tremendous thunder of the horses' hoofs, no doubt had a huge psychological effect.

The main problem with the knight was the expense. Their armor came at a high price, and when “chain mail,” as it was called, was found to be vulnerable to arrows, metallurgists had to go to work. Steel was soon developed, however, and small steel plates were placed over the chain mail. But even the steel plate eventually became vulnerable to the crossbow, and later to the longbow.

The crossbow fired steel bolts. The biggest problem with early crossbows was that it took a lot of strength to load them, and, as a result, they had a slow rate of fire. Later on, however, in the eleventh century, a mechanical winch system was added that overcame the problem of loading the weapon; furthermore, it allowed archers to create much more tension in the string, giving the bolt considerably more kinetic energy and velocity when it was released.

The drawback of the crossbow was that steel bolts were not as aerodynamic as arrows, and they were therefore less accurate. Nevertheless, the crossbow became a real threat to a knight armored only with chain mail.

The tactics of this period are seen in one of the most important battles to occur at the time: the Battle of Hastings, which took place in 1066. It was fought between an English army under King Harold II and a Norman army under Duke William II, and it took place about six miles from Hastings in England.
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The tactics of William proved to be much more effective than those of Harold. He had a force of archers, cavalrymen, and infantry working together; Harold's army was almost entirely infantry. Both men had about the same number of fighters—approximately twenty thousand. The English army, mostly infantry, used a conical metal helmet, a metal vest, and a shield; its primary weapon was the ax, but some of the men used swords.

William's army attacked first, shooting volleys of arrows, but most of them merely hit the shields of the English and had little effect. Believing this had weakened the English, William charged, but the English threw everything they had at his forces, and the English inflicted many casualties in hand-to-hand fighting.

Suffering heavy casualties, the Normans retreated. The English broke rank and followed them, and the fighting became fierce and confused. William's horse was killed and he toppled to the ground, but he was not killed. He somehow managed to rally his troops and counterattack, but he now realized that the initial hail of arrows had had little effect, so he ordered his archers to fire over the men with shields in the front line to target the unprotected rear ranks of the English army. This had a considerable effect. Indeed, Harold himself was struck in the eye by an arrow.