A bomb is conventionally an encased explosive or chemical, triggered by a fuse or by impact, that is used in warfare. Bombs can be flung by hand or through a barrel, propelled by a rocket, carried within a missile, dropped from an aircraft, or left in the ground or water as mines. In addition, bombs take effect in various ways: through fragmentation, which scatters bullet-like fragments such as shrapnel; through the heat and fire of incendiary bombs; through the destructive surge of air called the "blast"; through the suction after-effect of this displaced air; and through shock, which can convulse the earth, buildings, and water.
The history of bombs, intertwined with the history of war, extends far back in time. Catapults, which projected stones, arrows, or incendiary mixtures generally based on tar, date back to antiquity. The relatively late, petroleum-based incendiary mixture known as "Greek fire" was apparently first used by the Byzantines in the seventh century. The medieval trebuchet, which appeared around 1100, introduced the most important technical changes to the catapult.
The widespread exploitation in the 1300s of gunpowder, which had been developed much earlier by the Chinese, opened a new era in the history of bombs. As gunpowder burns explosively when heated, it can be detonated to hurl projectiles from wooden or metal barrels. Western use of the cannon dates from the 1320s, and soon became standard to European armies; the term "bomb" derives from the short-barreled cannons of this period known as bombarda. By the late 1500s, the Dutch began using bombs fired in high arcs through the use of short-barrelled mortars. These bombs were hollow metal balls filled with gunpowder; a fuse set into a small hole burned its way down to set off the explosion.
Aerial bombing was first attempted in 1849, when the Austrians deployed hot-air balloons loaded with small bombs against the city of Venice. These "bombers," carried by the wind, caused little actual damage but proved psychologically effective. They also foreshadowed the twentieth century use of aerial bombing, made possible by the invention of the airplane in 1903 and spurred by the advent of the two World Wars.
In a 1911 experiment, an American soldier hand-dropped a homemade, two-pound bomb from a Wright brothers airplane onto a test target on the ground. Later that year, an Italian army officer dropped four converted hand grenade s onto enemy forces from the air. By the end of the war, the Germans had used zeppelins to drop more than 200 tons of bombs on London, England. To do so, the Germans adapted conventional bombshells with better fuses and with fins for improved navigation.
Projectile bombs were also developed during World War I. The Germans wanted a weapon that could drop straight down into narrow trenches, which were a key arena of this war. They developed the Minewerfer, which was loaded manually and had both the barrel and the bomb rifled (grooved) to achieve the desired trajectory. Eventually, several countries designed automatic mortars; the bombs for these mortars had built-in percussion caps that, at impact with the bottom of the barrel, ignited the bomb's propellant.
Chemical warfare bombs, in addition, were primarily deployed during the first World War. The Germans began using poisonous chlorine gasbombs in 1915; soon both sides of the war had resorted to chlorine, mustard gas, and phosgene bombs--releasing horrendous gasses that destroyed human skin and lungs. Chemical warfare, though still intermittently deployed, is now largely proscribed. However chemical bombs were set to have been deployed by Iraq in the Persian Gulf War, and several other countries are known to possess chemical warheads.
Another type of bomb developed in World War I was the depth charge, designed by the British to protect their navy against the German U-boat (submarine), whose torpedoes could carry up to 220 pounds of explosives. Ironically, the torpedo had been invented and perfected by the British themselves in the second half of the nineteenth century. Depth charge bombs consisted of canisters filled with explosives and fitted with a valve triggered by water pressure against a spring; the tension of the spring could be adjusted to set off the explosive at the desired depth. The depth charge created a small lethal blast radius of about twenty-five feet for 300 pounds of dynamite (which was first manufactured in 1875); damaging shock waves extended much farther. Underwater mine bombs, though used by the Dutch as early as 1585, also became significant strategic weapons during the first World War.
It was World War II, nonetheless, that saw extensive advances in and deployment of bombs, which now weighed in at up to 2000 pounds. New fragmentation bombs were designed using metal wire wound around an explosive charge. Armor-piercing bombs were created with a thick case and a pointed tip to penetrate and explode inside of ships, tanks, and bunkers. Thinly-cased blockbuster bombs, which had little penetrating power but generated a powerful blast, were also developed. A new form of incendiary bomb generated intense heat through the burning of thermite, a mixture of aluminum powder and iron oxide, which in turn ignited a bomb casing made of magnesium.
One bomb created by the Germans during the second World War, the V-1, is often classified as a rocket. It was actually a jet-propelled, pilotless bomb with a powerplant known as a pulsejet. Its air-breathing engine operated intermittently, admitting air in pulses like modern turbo jets. This system saved on fuel, leaving the V-1 capable of carrying a one-ton warhead 300 miles from Germany to London. However, the relatively slow speed of this weapon, about 450 miles per hour, made it vulnerable to attack or neutralization by fighter planes. In several documented cases, Allied fighter pilots flipped the V-1 off its course by flying alongside the bomb and gently deflecting it with their wings.
Since the end of the second World War in 1945, bombs have undergone even further elaboration. Cluster bombs were developed for aerial use. These consist of an outer casing enclosing dozens of small bombs; the casing splits open in the air, releasing a shower of bomblets to explode upon contact. Fuel-air bombs release a cloud of volatile and explosive vapor close to the ground. Napalm bombs, a mixture of napalm and aviation fuel, scatter flaming gasoline in all directions. "Smart bombs," fitted with small wings, adjustable fins, and compact laser beam or video-remote guidance systems, have been designed for long-distance precision bombing. Some "smart bombs" are equipped with a "smart fuzes" that contains elaborate sensory equipment. For example such a bomb can sense when it has penetrated a buried structure such as a bunker, and then detonate itself. This type of bomb was used against Iraq in the Persian Gulf War, with mixed accuracy.
The most significant era in the history of bombs dates from the end of World War II, when the United States dropped the atomic bomb on the Japanese cities of Hiroshima and Nagasaki, starting the nuclear age. Since then, so-called hydrogen or nuclear fusion bombs have been created with hundreds of times the explosive power of the bombs dropped on Japan. Long-range delivery systems have also been developed so that targets thousands of miles distant can be hit. Though with the end of the Cold War, many people perceive that the danger of nuclear war has lessened, in fact nuclear bomb technology has spread to more countries, making disarmament a more complex and daunting process in the post-Cold War era.
Even relatively small and conventional bombs are capable of inflicting great damage, especially in a crowded urban area. Two deadly bomb attacks in the United States in the 1990s were attributed to small groups using easy to obtain materials. A bomb set off in the World Trade Center in New York City in 1993 killed six people and injured more than a thousand. The bomb was made in an apartment and conveyed in a van. A similar bomb, made of ammonium nitrate and fuel oil and ignited from a car, destroyed the Alfred P. Murrah Federal Building in Oklahoma City in 1995. Hundreds of people were killed and the nine-story building was destroyed in the attack, carried out by a pair of men. The relative simplicity of the technology and the availability of materials makes this type of bombing difficult to prevent.
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