Incendiary device
Incendiary weapons, incendiary devices, incendiary munitions, or incendiary bombs are weapons designed to start fires. They may destroy structures or sensitive equipment using fire, and sometimes operate as anti-personnel weaponry. Incendiaries utilize materials such as napalm, thermite, magnesium powder, chlorine trifluoride, or white phosphorus. Though colloquially often called "bombs", they are not explosives but in fact operate to slow the process of chemical reactions and use ignition rather than detonation to start or maintain the reaction. Napalm, for example, is petroleum especially thickened with certain chemicals into a gel to slow, but not stop, combustion, releasing energy over a longer time than an explosive device. In the case of napalm, the gel adheres to surfaces and resists suppression.
Pre-modern history
A range of early thermal weapons were utilized by ancient, medieval/post-classical and early modern armies, including hot pitch, oil, resin, animal fat and other similar compounds. Substances such as quicklime and sulfur could be toxic and blinding. Incendiary mixtures, such as the petroleum-based Greek fire, were launched by throwing machines or administered through a siphon. Sulfur- and oil-soaked materials were sometimes ignited and thrown at the enemy, or attached to spears, arrows or bolts, and fired by hand or machine. Some siege techniques—such as mining and boring—relied on combustibles and fire to complete the collapse of walls and structures.Towards the latter part of the period, gunpowder was invented, which increased the sophistication of the weapons, starting with fire lances.
Development and use in World War I
The first incendiary devices to be dropped during World War I fell on coastal towns in Norfolk, England, on the night of 19–20 January 1915, during a raid by the Imperial German Navy Zeppelins L 3 and L 4. These German firebombs were smooth metal canisters packed with kerosene- or benzol-soaked rope, sealed in resin to form a hardened incendiary core. Dropped from Zeppelin airships during raids between 1915 and 1917, these devices were designed to ignite fires upon impact. While some later designs featured stabilizing fins, many incendiaries used in early attacks had smooth exteriors, with the rope wrapping giving them a ridged appearance.The incendiary bomb's construction began with a hanger at the top, fitted with a cloth streamer to stabilize its descent. Beneath this was a metal cone supporting tightly wound coils of rope, reinforced with wire. A resinous material was poured over the rope and cone, forming a hardened outer casing once solidified. Inside, a central cylinder contained thermite—a pyrotechnic composition capable of reaching temperatures up to. The base of the bomb was a strong, saucer-shaped metal plate, pierced with air holes and designed to accommodate the lower end of the thermite cylinder.
One notable variant was the Goldschmidt Incendiary Bomb, named after Hans Goldschmidt, the inventor of thermite. This design measured approximately 50 cm in height and 18 cm in diameter, with a total weight of around 10 kg. It featured an inner metal cylinder filled with thermite, surrounded by a thin sheet metal container holding 3.5 litres of benzol. The outer shell was wrapped in tarred rope, which helped retain the benzol within the container and added to the bomb's flammability. This configuration enhanced the incendiary effect upon impact and was typical of the more destructive devices used in later Zeppelin raids.
On 8 September 1915, Zeppelin L 13 dropped a large number of firebombs during a raid on London. Although the devices were generally ineffective in terms of widespread destruction, the attack resulted in civilian casualties and had a significant psychological effect across England.
Following experiments with 5-litre barrels of benzol, the B-1E Elektron fire bomb was developed in 1918 by scientists and engineers at the Griesheim-Elektron chemical works. The bomb was ignited by a thermite charge, but the main incendiary effect was from the magnesium and aluminium alloy casing, which ignited at, sustained combustion at, and released vapour that burned at temperatures reaching. A further advantage of the alloy casing was its lightness—being a quarter of the density of steel—which enabled each bomber to carry a considerable number of bombs.
In the summer of 1918, the German High Command devised an operation called "The Fire Plan". It involved deploying the entire German heavy bomber fleet in successive waves over London and Paris, dropping as many incendiary bombs as possible until either the fleet was destroyed or the crews became too exhausted to continue flying. The objective was to engulf both capitals in an inextinguishable blaze, compelling the Allies to sue for peace. Thousands of Elektron bombs were stockpiled at forward bomber bases and the operation was scheduled for August and again in early September 1918. On both occasions, however, the order to take off was countermanded at the last moment, possibly due to fears of Allied reprisals against German cities.
Separately, a plan to firebomb New York with new long-range Zeppelins of the L 70 class was proposed by the naval airship fleet commander Peter Strasser in July 1918, but the proposal was vetoed by Admiral Reinhard Scheer, possibly due to concerns over strategic escalation or feasibility.
In contrast to German plans, the Royal Air Force had already deployed its own "Baby" Incendiary Bomb, which also contained a thermite charge.
Development and use in World War II
Incendiary bombs were used extensively in World War II as an effective bombing weapon, often in a conjunction with high-explosive bombs. Probably the most famous incendiary attacks are the bombing of Dresden and the bombing of Tokyo on 10 March 1945. Many different configurations of incendiary bombs and a wide range of filling materials such as isobutyl methacrylate polymer, napalm, and similar jellied-petroleum formulas were used, many of them developed by the US Chemical Warfare Service. Different methods of delivery, e.g. small bombs, bomblet clusters and large bombs, were tested and implemented. For example, a large bomb casing was filled with small sticks of incendiary ; the casing was designed to open at altitude, scattering the bomblets in order to cover a wide area. An explosive charge would then ignite the incendiary material, often starting a raging fire. The fire would burn at extreme temperatures that could destroy most buildings made of wood or other combustible materials.File: Ballroom Castle Warsaw September 17 1939.jpg|thumb|upright|left|Burning ballroom at the Royal Castle, Warsaw, as a result of incendiary bombing by the German Luftwaffe
The German Luftwaffe started the war using the 1918-designed one-kilogram magnesium alloy B-1E Elektronbrandbombe; later modifications included the addition of a small explosive charge intended to penetrate the roof of any building which it landed on. Racks holding 36 of these bombs were developed, four of which could, in turn, be fitted to an electrically triggered dispenser so that a single He 111 bomber could carry 1,152 incendiary bombs, or more usually a mixed load. Less successful was the Flammenbombe, a 250 kg or 500 kg high explosive bomb case filled with an inflammable oil mixture, which often failed to detonate and was withdrawn in January 1941.
In World War II, incendiaries were principally developed in order to destroy the many small, decentralised war industries located throughout vast tracts of city land in an effort to escape destruction by conventionally aimed high-explosive bombs. Nevertheless, the civilian destruction caused by such weapons quickly earned them a reputation as terror weapons with the targeted populations. Nazi Germany began the campaign of incendiary bombings at the start of World War II with the bombing of Warsaw, and continued with the London Blitz and the bombing of Moscow, among other cities. Later, an extensive reprisal was enacted by the Allies in the strategic bombing campaign that led to the near-annihilation of many German cities. In the Pacific War, during the last seven months of strategic bombing by B-29 Superfortresses in the air war against Japan, a change to firebombing tactics resulted in the death of 500,000 Japanese and the homelessness of five million more. Sixty-seven Japanese cities lost significant areas to incendiary attacks. The most deadly single bombing raid in history was Operation Meetinghouse, an incendiary attack that killed some 100,000 Tokyo residents in one night.
Image:stabbrandbombe inc 4 lb.jpg|thumb|British I.B. 4-lb. Mk IV type incendiary bomb. Top: complete device, nose is red. Middle: dud found without the tin plate tail. Bottom: the remains after burning. RAF Bomber Command dropped 80 million of these 4 lb incendiary bombs during World War II. The 4 lb bomb was also used by the US as the "AN-M50".
The incendiary bomb, developed by ICI, was the standard light incendiary bomb used by RAF Bomber Command in very large numbers, declining slightly in 1944 to 35.8 million bombs produced. It was the weapon of choice for the British "dehousing" plan. The bomb consisted of a hollow body made from aluminium-magnesium alloy with a cast iron/steel nose, and filled with thermite incendiary pellets. It was capable of burning for up to ten minutes. There was also a high explosive version and delayed high explosive versions which were designed to kill rescuers and firefighters. It was normal for a proportion of high explosive bombs to be dropped during incendiary attacks in order to expose combustible material and to fill the streets with craters and rubble, hindering rescue services.
File: Royal Air Force Bomber Command, 1942-1945. CH18371.jpg|thumb|left|Avro Lancaster bomb bay showing later mix of 4,000-pound "Cookie" blast bomb and 12 small bomb containers each containing 236 4 lb incendiaries.
Towards the end of World War Two, the British introduced a much improved incendiary bomb, whose fall was retarded by a small parachute and on impact sent out an extremely hot flame for ; This, the "Incendiary Bomb, 30-lb., Type J, Mk I", burned for approximately two minutes. Articles in late 1944 claimed that the flame was so hot it could crumble a brick wall. For propaganda purposes the RAF dubbed the new incendiary bomb the "Superflamer".
Around fifty-five million incendiary bombs were dropped on Germany by Avro Lancasters alone.
Many incendiary weapons developed and deployed during World War II were in the form of bombs and shells whose main incendiary component is white phosphorus, and can be used in an offensive anti-personnel role against enemy troop concentrations, but WP is also used for signalling, smoke screens, and target-marking purposes. The U.S. Army and marines used WP extensively in World War II and Korea for all three purposes, frequently using WP shells in large 4.2-inch chemical mortars. WP was widely credited by many Allied soldiers for breaking up numerous German infantry attacks and creating havoc among enemy troop concentrations during the latter part of World War II. In both World War II and Korea, WP was found particularly useful in overcoming enemy human wave attacks.