The Physics of War (8 page)

For years Genghis Khan, the leader of the Mongols, had been eyeing China. It was prosperous and thriving, and the Chinese had many things that the Mongols wanted and needed. In 1205, Genghis Khan decided to attack. It was little more than a raid, but it frightened and panicked the Chinese. The Mongols were cruel and well known for their use of terror; they took no prisoners and frequently wiped out entire villages.
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The Chinese had to do something, and they had to do it fast. They needed a weapon to counter the Mongols, and indeed they had something with considerable potential: a white powder that they were using in their fireworks.

Genghis Khan attacked again in 1207, causing even more fear. This attack spurred the Chinese to develop what would become known as the “fire lance.” It was a bamboo tube several feet long that had been drilled through the joints, with the bottom joint left in. The tube was wrapped to reinforce it and a small “touchhole” that could be used as a fuse was drilled near the lower end. White gunpowder was poured into the bottom, and arrows or other projectiles were placed on top of it. When the gunpowder was lit through the touchhole, the arrow left the barrel with considerable speed, but it only had a range of about ten feet. They also developed other weapons, such as simple flamethrowers, rockets of various types, bombs that could be thrown with a catapult, and land mines.

The Mongols declared full war in 1211 and swept down on horseback by the thousands, but the Chinese fought gallantly with everything they had. For two years the Chinese held them off, but eventually the Mongols overcame them, and soon they were using the new Chinese weapons against others.

Over the next few decades the art of war changed significantly. A revolution had begun, but at this time no one realized how important gunpowder would eventually become in warfare. To tell the entire story, however, we have to begin with the discovery of the components of gunpowder, one of the most important
of which is saltpeter. Saltpeter is actually potassium nitrate, and at the time of the Mongol invasion it was relatively rare in China. One of the first places it was found was on the walls of caves, where it could be scraped off as a white crystalline powder. It generated interest because it flamed up when sprinkled on a fire. Later it was also found on the floor of stables that housed horses. Alchemists showed that it came from the urine of horses.

Genghis Khan.

The biggest problem with the early form of saltpeter was that it was actually a mixture of potassium nitrate and calcium nitrate. Techniques for improving its purity were developed over the years by alchemists, and they eventually became interested in it as a possible elixir of immortality. In the early 800s, however, they began mixing it with other chemicals. A mixture that soon began to attract interest was the mixture of saltpeter, sulfur, and carbon (in the form of charcoal). When rolled in paper and set on fire it caused a loud explosion, and as a result it was soon used in celebrations and to scare away evil spirits.

The Chinese alchemists no doubt started with a 1:1:1 mixture of the three materials, but they eventually found that a 4:1:1 mix (with the 4 corresponding to saltpeter) gave a much better explosion. As it turned out, saltpeter was the oxidizer in the combination (so it didn't need air to explode), with sulfur and carbon acting as fuels. The ratio between the three components was, indeed, critical, and it was later found that different ratios yielded even greater explosions. For gunpowder, however, the three major components remained the same.

For a few hundred years after the discovery of gunpowder there is no indication
that the Chinese used it for anything but celebrations and as “toys” for children. But all that changed when the Mongols attacked. At first they overcame a few villages in the north, but finally they not only conquered all of China, but also continued on their rampage throughout Europe, eventually capturing most of it. And not only did they use the new Chinese weapons, but they developed others and used them in their further conquests.
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News of the new weapons spread rapidly. By 1250 the Arabs had begun to use gunpowder in a simple “cannon” they called the madfaa. It consisted of a wooden bowl or pot that was packed with gunpowder, with arrows or other projectiles such as stones above it. When the fuse was lit the arrows or stones would fly in the general direction of the enemy. Needless to say, the madfaa was very inaccurate.
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ROGER BACON

The news of the strange new explosive eventually reached England in the mid-1200s, and an English philosopher and Franciscan friar named Roger Bacon heard about it. A trader or missionary brought him a “firecracker” that had been made in China. Bacon had a strong interest in science; indeed, he eventually made significant contributions to many branches of science and mathematics, including optics and astronomy. Furthermore, he had a relatively good knowledge of chemistry. He took the firecracker carefully apart and examined the powder inside. Analyzing it, he found it to be made up of saltpeter, sulfur, and charcoal, and it didn't take him long to realize it was an important mixture that could have significant application in war. He worried that it might get into the wrong hands; nevertheless, he mentioned the discovery in his book
Epistolae de Secretis Operibus Artis et Nature et de Nullitate Magiae
a few years later, though he was reluctant to publish the exact formula for it. It is said that he finally decided to publish it in the form of a cryptogram, but others have disputed this.
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One of the problems with gunpowder at this stage was that it depended critically on saltpeter, and Bacon soon discovered that the saltpeter in the mixture was impure. He therefore made a study of it and found a way to purify it.

While Bacon was making his discoveries, the Chinese were still working on their weapons. Within a few years they had developed a crude form of a cannon, but at this stage it was difficult to use and dangerous when fired. And, of course, their crude cannons were terribly inaccurate. They noticed, however, that if the explosive gases were contained in a fireproof and blast-proof chamber, the resulting “explosive power” was significantly increased.

Evidence that the Chinese were working on gunpowder came in 1280 when a large gunpowder arsenal caught fire. The resulting explosion was heard for miles around, and it was reported that over one hundred guards were killed in the explosion. Furthermore, pieces of the storage building were found over two miles from the explosion.

DEVELOPMENT OF THE CANNON

Crude early cannons were made by the Chinese, the Arabs, and the Mongols, but the first cannons as we know them appear to have been built in Germany and Italy. The name
cannon
, incidentally, comes from the cylindrical barrel of the device; the Latin word for it is
canna
. The Latin word
canon
was also used later to mean “gun.”
⁵

An early Chinese hand cannon.

The first English cannon appeared in 1327, and there is some indication that the German Berthold Schwartz (sometimes called “Black Bart”) mixed up the ingredients of gunpowder about this time and may have made a simple cannon. According to folklore, he put his mixture in a pot and covered it with a large stone slab, and somehow a spark ignited it and blew the large slab through the roof of his laboratory.
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In 1326 the first drawing of a cannon appeared in a book by Walter de Milemete. And in 1341 a poem titled “The Iron Cannon Affair” was published by Xian Zhang. He wrote that a ball fired from a cannon could “pierce the heart or belly…and can even transfix several persons at once.”
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Cannons were still relatively rare in Europe in the 1340s, however, and they still shot only arrows and grapeshot. In some cases the arrows were aflame in flight. Furthermore, in the earliest cannons the gunpowder was a fine powder and the resulting explosion was not impressive. Indeed, only a fraction of the gunpowder actually exploded. The gunpowder was placed in a cylinder of bronze or iron, which was closed at the lower end, with the cannonball placed on top of it. Large stones were initially used as cannonballs, but iron balls eventually replaced them. They were spherical because of their tumbling motion in flight. The gunpowder was ignited through a touchhole. In a sense it was a fuse, but it actually consisted of a narrow stream of gunpowder. When the gunpowder mixture was ignited it quickly changed from a solid to a gas, which increased its volume by a factor of about four thousand. The gas was highly compressed and created a tremendous force as it expanded, pushing the cannonball down the barrel.

A lot of science and technology is required in the building of a cannon. Metallurgy is important in the building of the cannon barrel and housing; chemistry is important in determining the best mixture of materials for the gunpowder and how much to put in the cannon. Too little and the ball will not go far; too much and the cannon will explode, killing anyone near it. In these early years, in fact, many soldiers were killed by exploding cannons.

The drill that a cannon crew went through each time a shell was fired was somewhat as follows:

a)   The correct amount of gunpowder had to be poured in the barrel, and it had to be tamped down.

b)   A wad or plug was usually placed over it.

c)   A cannonball was placed in next and pushed firmly against the pad.

d)   Gunpowder was poured in the touchhole.

e)   A flame was brought up to the touchhole.

THE HUNDRED YEARS' WAR

The cannon was first used by the English in the Hundred Years' War, which started in 1337 and ended in 1453. It was a long war that was fought off and
on between the French and English. Most people remember it for the important victory of the French over the British when the French were led by Joan of Arc, a seventeen-year-old peasant girl who was burned at the stake when she was only nineteen.

Cannons were used very little in the early years of the war. At this stage they were still inferior to siege engines; they couldn't penetrate castle walls, and they had many problems. By the time of the last battle at Castile in Gascony in 1453, however, cannons had been improved significantly, and they proved to be quite effective. Three hundred cannons were used in this battle.

THE BASILICA AND THE SIEGE OF CONSTANTINOPLE

Cannons also played a critical role in one of the most important battles of this period—the battle that led to the downfall of Constantinople in 1453. For years there had been tension between the Ottoman Turks and the Byzantine Empire. Then, in 1451, Sultan Mehmed II came to power. Many thought he was too young to be taken seriously, but he soon proved them wrong. Within two years he had a large army and was preparing to attack the Christian stronghold at Constantinople, a city that was protected by a huge fifteen-mile-long wall that was thought to be impregnable.
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But Mehmed was determined. Under his direction, one of the largest cannons ever built, called
Basilica
, was constructed. It was designed and built by a Hungarian engineer by the name of Urban. Little is known about him, but there is no doubt that he knew a lot about cannons. Initially, Urban offered his services to Constantine XI of Constantinople, but he was turned down (records indicate that his asking price was too high), so he went to Mehmed and the Ottomans and they accepted his offer.