Military aircraft designed with the primary mission of dropping bombs.
Bombers are generally classified by the type of bomb they deliver (a torpedo-bomber delivers a torpedo), their size (light, medium, or heavy), or their mission (fighter-bomber). While World War II saw a wide variety of bomb-dropping aircraft, the number of distinct bomber types produced has dwindled, as newer aircraft, such as fighters that are tasked with bombardment missions, perform multiple roles.
The first military aircraft were used for reconnaissance. Only after trench warfare began did generals come to see airplanes as platforms that could carry ordnance beyond enemy lines to strike specific targets. In order to successfully bomb targets, bombers had to carry bomb loads that were heavy enough to inflict significant damage, to fly both high and quickly enough to bypass enemy defenses, and to deliver bombs accurately enough to hit the desired targets.
In order to build successful bombers, aircraft manufacturers had to overcome many technical difficulties that limited aircraft capabilities and performance. It is difficult, for example, to drop a bomb from a moving airplane so that it arrives on target, especially if the target is obscured or camouflaged. Bombs must be able to penetrate deeply enough or must carry enough explosive force to destroy the target. Bombers must be capable of flying high enough or quickly enough to avoid enemy fire or must be armored well enough to render enemy fire ineffective. Although defensive armor increases a bomber’s odds of survival, its greater weight limits speed, range, and bomb load. Better accuracy is found at lower speeds and altitudes, where bombers are more vulnerable. A longer range allows bombers to hit a greater variety of targets but requires more fuel and, thus, a lighter bomb load. Finally, bombers require defensive armaments, or weapons, to avoid being shot down by fighters.
World War I saw experiments with almost every possible bomber mission. The first bombs were simply grenades tossed at enemy positions. Because these weapons were too light and inaccurate to cause serious damage, heavier bombs were designed. Early bombs that were released over the side of an airplane were often inaccurate. The first bombers were observer aircraft converted for bombing missions. To inflict serious damage, many bombs were needed, so bombers began to fly in groups. Enemy fighters also forced bombers to fly together to mass their defensive firepower. By 1917, both sides had introduced specialized, bomb-carrying aircraft. The German Gotha G-IV, for example, was designed to attack enemy cities or port facilities far behind the battle lines. Fighters or observation planes were assigned to attack frontline headquarters or troop concentrations. Britain’s Royal Navy Air Corps also experimented with launching planes from ships and, thus, introduced the aircraft carrier.
Although World War I bombers flew many varied missions, these operations were more ad-hoc responses to opportunities or threats than they were planned innovations. After the war, airmen began to develop theories about how aircraft could change the nature of war. The most famous of these was Italian general Giulio Douhet, who predicted that bombers could fly over battlefields to avoid costly ground battles. Bombers could attack specific cities, which Douhet termed a nation’s “vital centers.” Bombing would result in such damage and terror that citizens would force their governments to sue for peace. This terror bombing was justified as being more humane and less costly than the losses and suffering caused by a protracted war such as World War I. Essential to Douhet’s theory was his claim that bombers would always perform as well as fighters, would carry more armament, and could thus always get though to their targets.
In the United States, General William “Billy” Mitchell, a strong advocate of air power, embraced Douhet’s ideas, because they seemed to justify the creation of a separate branch of service. Mitchell believed that only a new and independent organization would be free from traditional preconceptions and could, thus, be innovative in utilizing new technologies.
Improved engines and metallurgy allowed aircraft designers to create weapons tailored to suit Douhet’s predictions. Especially significant was the United States’ adoption of the Norden bombsight, a complex instrument that was, in effect, an early analog calculator linked to an autopilot that determined the appropriate bomb release point using altitude, speed, and bomb type. Once the bomber was situated over the target, the bombsight automatically released the bombs at precisely the correct point, which could easily be missed by a pilot’s human error.
Naval aviators perfected dive-bombing as another method to increase accuracy. A bomber would dive toward the target and release the bomb at the last possible instant before the aircraft pulled out of the dive, so that the bomb’s trajectory was an extension of the dive. Dive-bombing was very accurate and was especially useful against maneuvering ships.
During World War II, many specialized types of bombers were used on missions that included strategic bombing, air superiority, interdiction, and tactical air support. In each case, bombers proved useful but neither as invulnerable nor as decisive as Douhet had predicted. Airframe and power plant developments resulted in fighters of great speed and heavy armament. Massed fighter attacks against bomber formations inflicted terrible damage on bombers that had to fly straight during their final bomb runs.
Technological advancements also increased the lethality of antiaircraft artillery. By 1945, antiaircraft defenses had been developed that used radar to determine the altitude and bearings of incoming aircraft, and proximity fuses ensured airbursts near the bombers. To avoid the more potent antiaircraft defenses, bombers were flown at higher altitudes that rendered them less accurate. During the war, more than one-half of the bombs dropped landed more than 1,000 feet from their targets.
Bomber enthusiasts failed to anticipate the effectiveness of what are now called passive defenses. Camouflage, decoy targets, smoke screens, and blackouts obscured targets and often rendered bombing raids ineffective, and civil defense measures reduced damage. Civilian morale proved more resilient than expected; terror attacks angered rather than intimidated civilians. Modern, organized national economies could thwart strategic bombing attacks by utilizing more civil defense personnel and replacement laborers or by dispersing factories to make them less vulnerable. These tactics made the concept of vital centers too vague to be useful. Throughout the war, airmen sought to destroy specific enemy industries, such as ball-bearing plants or petroleum refineries, which when destroyed, might cripple the enemy’s ability to continue the war. Although these efforts inflicted terrible damage and chaos, enemy economies did not collapse.
Strategic bombardment also suffered from dispersal of effort. Anglo-American airmen such as U.S. general Henry Harley “Hap” Arnold faced continued demands for the diversion of bombers to other missions. Navies wanted long-range bombers for extended antisubmarine or reconnaissance missions. Theater commanders called for air assets to be used to interdict the movement of enemy troops and supplies, while battlefield commanders cried for tactical air support. After the war, air power theorists would claim that their lack of success was driven by these diversions.
The German experiences in World War I and the Spanish Civil War indicated that strategic bombardment alone would not bring victory. Many German airmen had been infantrymen in World War I and saw bombardment and observation as great force multipliers for ground attacks. As a result, German doctrine demanded heavy attacks on enemy air bases after which most of the bombers would support battlefield actions instead of attacking enemy cities. German bombers also tended to be of medium range and tended to use dive-bombing for accuracy. Early in the war, the Germans were successful with this strategy, but as the Allies introduced improved fighters and tactics, German bomber losses began to climb. Nevertheless, the German tactics, based upon a combination of mobile ground units and tactical air support, proved very potent. By 1943, the British and American air forces began to develop their own methods of tactical air support, which, by the summer of 1944, had proven to be a crucial factor in Germany’s defeat.
World War II saw the invention of many technologies that would shape bombing missions and capabilities into the twenty-first century. Germany’s emphasis on ground attacks led to improved communications between the bombers and ground forces. Specialized ground-attack bombers were created, and standard bombers such as the Stuka were modified for improved ground-attack lethality. To improve accuracy, the Germans introduced guided bombs, which were successful on numerous occasions. The V-1 rocket was a pilotless rocket-driven bomb that anticipated the American cruise missiles of the 1980’s and 1990’s. Germany fielded the world’s first operational jet bomber when it introduced the Arado 234 Blitz Bomber.
Allied designers also introduced groundbreaking bomber technologies, inventing effective radar guidance systems to overcome the difficulty of finding targets. In order to stifle German antiaircraft defenses, the British invented what became known as chaff, thin strips of aluminum foil, which, when dropped in bundles, reflected aircraft-sized radar images that confused German gunners and night fighters. The Allies also introduced faster and more powerful bombers, including very-long-range strategic bombers, the most well known of which was the U.S. B-29 Superfortress.
Specialized bombs, such as the “Tallboy,” which was designed to maximize penetration of hardened targets and used on German U-boat pens, were created. Ultimately, the greatest and most complex bomb used was the atomic bomb. Although some historians argue that the Japanese surrender was due to more than just the dropping of the atomic bombs, atomic weapons came closer than any other weapon to realizing Douhet’s vision.
At the end of World War II, the United States investigated the effectiveness of bombing in a study called the United States Strategic Bombing Survey. According to the survey, bombing achieved a mixed record. Although strategic bombardment had not induced a complete collapse of the enemy, it had clearly played a major role in the Allied victories. Reflecting these results, postwar air forces became more balanced organizations. The U.S. Air Force, for example, divided bombing duties between Strategic Air Command (SAC), which operated long-range bombers armed with atomic bombs, and Tactical Air Command (TAC), which provided close air support for ground forces.
Throughout the second half of the twentieth century and into the twenty-first, bombers continued to play an active role in conflicts around the globe. New technologies made bombers increasingly powerful and more difficult to destroy. Some developments, such as jet engines and radar guidance systems, offered significant improvements over technologies introduced during World War II. Others, such as stealth technology, were entirely new. Stealth technology uses special aerodynamic shapes, radar-absorbing paint, and specially textured surfaces to render planes nearly invisible to radar.
The effectiveness of such technology was shown during the 1991 Persian Gulf War and the brief 1999 air campaign over Kosovo, where stealth aircraft penetrated enemy air defense zones. The effectiveness of bombers has also been enhanced by the development of powerful missile armaments and precision-guided munitions. In the 1982 Falkland Islands War, for example, French Exocet air-to-ground missiles sank a destroyer and damaged a number of British ships. In both the Gulf War and Kosovo, air-launched smart missiles guided by either infrared or radar inflicted considerable damage.
Both conventional bombers, such as the B-52, and stealth bombers can launch precision-guided munitions. The success of operations over Kosovo has resurrected the debate over the use of strategic bombardment as an alternative to ground warfare. While some claimed Kosovo was history’s first successful independent air campaign, evidence indicates that bomb damage was not as extensive as claimed and that diplomatic factors were as decisive as bomb damage in Serbia’s decision to surrender.
Corum, James S. The Luftwaffe: Creating the Operational Air War, 1918-1940. Lawrence: University Press of Kansas, 1997. Provides an insightful overview of how Germans developed their doctrine of tactical air support. McFarland, Stephen L. America’s Pursuit of Precision Bombing, 1910-1945. Washington, D.C.: Smithsonian Institution Press, 1995. Describes in detail the American efforts at achieving a war-winning strategic bombing campaign. Sherman, Don. “The Secret Weapon.” Air & Space Smithsonian 9, no. 6 (February/March, 1995). Describes the history of the Norden bombsight. Wildenberg, Thomas. Destined for Glory: Dive Bombing, Midway, and the Evolution ofCarrier Airpower. Annapolis, Md.: Naval Institute Press, 1998. An excellent history of America’s development of dive-bombing techniques and the use of aircraft carriers to project air power across the oceans.
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World War II
A World War II B-17 bomber departs after successfully hitting its target.