Chapter 17: Fire From the Air
Aerial incendiaries probably caused as much death and destruction as any other weapon used in World War II. Certainly they were the most important chemical munitions employed, considering their contribution in bringing the war to a successful conclusion. The record of these munitions is all the more remarkable because most of them were investigated, designed, and developed after the United States had entered World War II. Aerial incendiaries, for practical purposes, may be divided into two categories: the incendiary bomb, usually dropped by bomber aircraft on targets far behind enemy lines, and the fire bomb, a type which fighter-bombers used against targets at or near the front. Of the two, the incendiary bomb was by far the most important.1
The Incendiary Bomb: The Strategic Weapon
Pre-World War II Developments
The aerial incendiary was used for the first time in World War I. The earliest German incendiaries, dropped on England from zeppelins and airplanes, were shaped like buckets and consisted of a core of thermite wrapped with tarred cotton waste and tarred rope. These crude bombs were unsatisfactory both in incendiary action and ballistic quality. A torpedo-shaped bomb filled with gasoline and paraffin replaced the bucketlike munition, and before the end of the war German scientists had perfected the electron bomb. This 2-pound bomb was composed of a magnesium-thermite filler in a magnesium alloy casing. Though not used in World War I, it is nonetheless
important as the prototype of a very effective group of World War II incendiaries.2
Great Britain’s principal incendiary bomb, the Baby Incendiary, weighed but two-fifths of a pound. Filled with a special thermite mixture these small bombs were carried in containers capable of holding either 272 or 144 units. Great Britain used few of its Baby Incendiaries during World War I, although these bombs were in production and were found to be effective.
The United States developed several types of incendiary bombs during World War I. Two bombs, the Mark II and Mark III, were of the intensive type, that is, munitions with a high degree of penetrability and an intensive incendiary action. Both bombs contained a thermite charge which ignited the main incendiary, solidified oil. They differed mainly in size, and hence penetrability; the former weighed approximately forty pounds and the latter about too. The Mark I, a scatter-type bomb, was intended for use against very inflammable targets. In outward appearance the Mark I resembled the Mark II bomb, but, whereas the latter was filled with solid oil, the Mark I contained a number of waste balls saturated with an inflammable mixture. Two explosive charges ignited these pellets and cast them for a radius of twenty feet.
The United States also developed two incendiary darts, the impetus for which came from the success of the British with their Baby Incendiaries. The first American dart, the Mark I, consisted of an elongated 12-gauge shotgun shell filled with an incendiary material. This munition, which ignited on impact, was designed for use against grain fields and forests. The heavier Mark II dart, composed of a zinc body, a thermite and solid oil filler, and a steel nose, possessed the penetrability needed in a munition to be used against buildings.
Neither the incendiary darts nor the other three American aerial incendiaries saw use in combat. United States air units in France used a French munition, the Chenard, reported to be the most efficient of all Allied incendiary bombs.3
There was little interest in the United States in an incendiary bomb program during the period between the two World Wars. This neglect resulted largely from an overly optimistic evaluation of the capabilities of high explosive (HE) bombs. In 1934 an Ordnance Department study on the relative effectiveness of incendiary and demolition bombs concluded that “everything that can be accomplished by an incendiary bomb can, in most cases at least, be accomplished as well or better by either a smoke bomb loaded with white phosphorus (WP) or a demolition bomb loaded with a high explosive.4
There was one authoritative voice which did call attention to the possibilities of the incendiary bomb. Colonel Zanetti, a CWS Reserve officer on the faculty of Columbia University, insisted several times in the 1930s that the incendiary bomb had a great potential. Colonel Zanetti had worked with these munitions in World War I and had become perhaps the greatest American technical expert in the field. In 1936, when some people were dwelling on the horrors of aerial gas attacks in cities, he graphically pointed out that fire, not gas, was the greatest danger:
The small size of these [incendiary] bombs may appear almost ridiculous, particularly after considering the tons of gas that are required to produce lethal concentrations; but here comes the essential difference between gas and incendiaries that makes fire far more dangerous to a large city. Gas dissipates while fire propagates. Each of these small bombs held within itself the devastating possibilities of Mrs. O’Leary’s cow.5
Moreover, the Army Air Corps was becoming increasingly interested in the potentialities of the incendiary bomb. As early as November 1934 the commandant of the Air Corps Tactical School at Maxwell Field, Ala., recommended to the Chief of Air Corps a project aimed at developing a filling for an incendiary bomb, and one month later he sent the Chief, CWS, the military characteristics for such a munition. By April 1936 the CWS Book of Standards showed a military requirement for an incendiary filling for the 25-pound chemical bomb, and on 30 December 1936 the CWS established a project to find an
incendiary bomb filling.6 Despite these preparations, the eve of the United States’ entry into World War II found it with only one standardized incendiary bomb, the gasoline filled, 100-pound M47. This situation existed because of the continuing belief in the superiority of high explosives over incendiaries.7
The outbreak of war in Europe called attention as never before to the possibilities of aerial incendiaries. German planes began to shower London with magnesium electron bombs and I Io-kilo oil bombs, and the English replied with their 4-pound magnesium munition. The United States Army could no longer afford to neglect the development and production of incendiary bombs.8
In July 1941 General Porter, Chief, CWS, recalled Colonel Zanetti to active duty and sent him to London to obtain firsthand information on the research, development, and production of the British 4-pound incendiary bomb. Colonel Zanetti returned with formulas for fillings, blueprints for casings, and procedures for manufacturing, and a period of extensive work on aerial incendiaries ensued.9 But there was still a roadblock to be overcome. Since 1920 the responsibility for incendiary munitions had been divided between the Ordnance Department and the Chemical Warfare Service. The former had charge of the procurement of the containers and the storage and issue of the complete incendiary bomb whereas the latter developed the incendiary material and filled the munition.10 General Porter strove to consolidate the incendiary mission under the CWS. His last two assignments, before he became Chief, CWS, had been with the Army Air Corps so that he was fully aware not only of the value of aerial incendiaries but also of the necessity for their undivided control. The argument for a unified responsibility was especially strong in the case of the magnesium bomb for the container and incendiary material were one and the same.11
In September 1941 the CWS received the complete responsibility for the entire incendiary bomb program.12
Experiences of the Eighth Air Force
Most new weapons and munitions initially experience difficulty in gaining the confidence of the using arm, and the incendiary bomb proved no exception. Moreover, the early bombs produced by the CWS were far from perfect, an understandable situation when it is realized that most of the work was done in the hurry and bustle after the United States entered World War II. Factors favoring the munition, among which were Germany’s success with and Great Britain’s respect for aerial incendiaries, did little to lessen the Air Corps’ initial apathy, particularly at operational levels.
The British realized the merits of incendiary bombs much sooner than did the United States, for not only had they entered the war earlier but their cities had been targets for bombing raids of the German Luftwaffe. Almost immediately Great Britain established an operational research organization, known as RE/8 (Research and Experiment Station, Section 8), under the Ministry of Home Security. Gathered together there were scientists, statisticians, photo interpreters, and other experts whose duty it was to study the effects of bombing. American personnel, military and civilian, were soon attached to this division whose findings were available to both British and American air commanders.13
RE/8 scientists soon found that, in attacks against the industrial cities of Germany, properly employed incendiaries were more efficient
than high explosives.14 The Royal Air Force in a series of raids against Hamburg in the summer of 1943 went a long way in establishing the validity of this conclusion. Between 24 July and 3 August the RAF, at times supplemented by American bombers, attacked that German city seven times, proving beyond all doubt the destructive power of the incendiary bomb. Almost 1½ million bombs were dropped on Hamburg, the large majority (1 1/3 million) being 4-pound incendiaries.15 German officials stated that 45,000 people lost their lives, although this number was admittedly inaccurate: “Exact figures could not be obtained out of a layer of human ashes.”16 Of the 122,000 houses standing before the raids, 35,719 were demolished and 4,660 were heavily damaged.17
Despite the British success with incendiaries, the Eighth Air Force remained unconvinced of their efficacy. Colonel Kellogg, the first chemical officer of the Eighth Air Force, played an important part in convincing his organization of the usefulness of incendiary bombs. A group of RAF officers who had extensive and successful operational experience with incendiaries vigorously supported his cause. These same RAF officers sparked the organization of an informal American-British discussion group, known as the Zoroastrian Society, which materially aided the Eighth Air Force in defining the nature and characteristics of incendiaries possessing the greatest potential. Meanwhile, both the RAF and the Eighth Air Force carried on an extensive program of munitions trials. As a result of these trials, the U.S. 6-pound incendiary oil bomb, the M69, was rejected and the British 30-and 250-pound incendiaries were accepted as interim weapons pending
the availability of more suitable American bombs and clusters. The most desired U.S. munitions in the early period were the 100-pound cluster of 4-pound magnesium bombs and the 100-pound M47 bomb with an oil and crepe rubber filling. But these desires could not readily be translated into supply since much of the process of development and manufacture had yet to take place in the United States.18
The first 100-pound clusters of the M50 bombs arrived in England. in 1942. This triumph of adequate supply was short-lived; chemical officers found a great many defective M50s in these early shipments and started a testing program to determine the bad lots. Defective bombs were only part of the problem. The 100-pound incendiary bomb adapter, which clustered the M50s into a convenient package, was operationally unusable because of the danger of released adapter parts striking other planes in the formation or even, in some cases, the tail of the plane that carried it. This was dramatically revealed during the Eighth Air Force’s first use of incendiary bombs on 14 May 1943, when falling cluster parts damaged other planes in the formation. Moreover, it was impossible to obtain any degree of accuracy with bombs released from their clusters at such high altitudes. Because of these deficiencies Eighth Air Force suspended the use of the M50 pending receipt of aimable clusters.19
Until the adequate clustering device for the M50s appeared, the Eighth Air Force relied to a great degree on the M47. This versatile 100-pound bomb (it actually weighed only sixty-nine pounds) was the sole American aerial incendiary available when the United States entered World War IL In a desperate attempt to provide incendiaries, Colonel Kellogg late in 1942 located a supply of empty M47 bomb casings in Iceland, managed to get them shipped to the United Kingdom, and had 10,000 filled and assembled by air chemical units. At first the M47 contained unthickened gasoline or oil, but later a thickener was added. The outstanding features of the munition were its aimability, penetrability, and its sizable load (forty pounds) of incendiary material. But the M47 also had its problems. While the munition itself was effective, bomb bay suspension arrangements were such that one bomb
occupied a space which could carry a much heavier bomb. By July of 1943 the air chemical sections provided a field expedient to solve this loading difficulty. They paired the bombs by the use of a cable loop-sling. The loop-sling method permitted the suspension of forty-two M47s in a B-17 bomb bay. This was an economical load, and the number of bombs falling together improved the bombing pattern. Furthermore, clustering supplies were readily obtained since the Eighth Air Force prepared slings in the great air repair depot at Burtonwood. Subsequently, Colonel Baum, who succeeded Colonel Kellogg as Eighth Air Force chemical officer in 1943, modified the loop-sling into a short cable toggling device which permitted the suspension of fifty-two bombs in a bomb bay and in effect made an enormous cluster of M47s which was more aimable and made a better bombing pattern.20
In the spring of 1943 Eighth Air Force headquarters requested mixed loadings of incendiary and high explosive bombs in a single aircraft on operational missions. The VIII Bomber Command declared this request unfeasible because uneconomical loads would result and because of the danger of mixing the two munitions in the same aircraft. The chemical officers agreed with the bomber command on mixed loadings but renewed their proposals of incendiary loads in view of the new development with respect to the M47. During the summer, Colonel Kellogg persuaded Col. Curtis E. LeMay to authorize M47 incendiary loadings for missions against industrial targets in occupied France. These missions conclusively demonstrated the effectiveness of incendiary bombing in general and the M47 incendiary in particular. Although a lack of fuzes caused the suspension of the employment of M47s for a month during this critical period, the Eighth Air Force was now firmly committed to the use of incendiaries, and the outstanding success of the first major incendiary raid in October, against a factory at Heddernheim, Germany, reinforced that decision. The Eighth Air Force analysis of the Heddernheim mission indicated that the incendiaries were far more effective, weight for weight, than high explosives.21 For the next three months, the M47 was the favored incendiary, and keeping a supply on hand became a major problem as all
incendiary expenditures mounted from 408.2 tons in September 1943, to 1,292.6 tons in October, 2,382.9 tons in November, and 4,189.6 tons, 40 percent of the total bomb load, in December.22
The M17 500-pound cluster for the M 50 bomb was first put into operational use in January 1944. This aimable cluster eliminated most of the difficulties inherent in those clusters which were quick opening and made the M50 one of the most effective incendiary bombs of World War II.23 An M50 (technically the AN-M50A1 and later the AN-M50A2) was a 4-pound bomb based on the plans brought back from England by Colonel Zanetti. Consisting of a core of thermate and a casing of magnesium alloy, the M50 had a high degree of penetrability and an intensive burning action. These qualities made it particularly suitable for use against construction in Germany, 95 percent of which consisted of brick and stone.24 Because of this construction, fire divisions (that area which will be burned out by an unchecked fire) could be not only buildings but their individual rooms. The M50 had to have great penetrating power in order to pierce the heavy roofs, and the fact that it was small meant that a bomber, in seeking out the numerous fire divisions, could carry many more than if the bomb were larger.
In direct contrast with the M50 was America’s largest incendiary bomb, the 500-pound M76, popularly known as the Block Burner. The M76 resulted from an Army Air Forces request for a large, highly aimable incendiary bomb for use against industrial targets. It contained incendiary gel (PT) which, upon the detonation of an explosive charge, was scattered in large gobs over a 100-foot radius. The M76 was used against Berlin on 6 March 1944 with moderate success, enough at least to warrant a request from the Eighth Air Force to the zone of interior for a priority shipment of these heavy incendiaries. Subsequent operations, however, proved that the efficiency of the bomb did not warrant its employment. Because of its size, there were relatively few targets against which it could be used. Moreover, there was a low percentage of incendiary fuel as contrasted with the total weight of the bomb. By September, because no future operational use of the M76
Loading 500-pound clusters of magnesium bombs into a B-24 of the Eighth Air Force, somewhere in England.
was anticipated, the stations of the Eighth Air Force had returned most of their M76 bombs to Air Forces depots.25
All together the Eighth Air Force dropped 97,046 tons of incendiary bombs on German targets compared with 569,751 tons of high explosives and 20,352 tons of fragmentation bombs. The large majority of the incendiaries were M50s, in M17 clusters, and M47’s.26 Taken as a reflection of the role of the incendiary bomb in the Eighth Air Force’s campaigns against Germany, this figure is little more than modest. The RAF expended many more aerial incendiaries than did the American air unit. To explain this, the essential difference between the two air forces must be borne in mind. The RAF was devoted to a policy of night, area raids against the cities of Germany. The Eighth Air Force,
on the other hand, confident in its bomb sight and in the protection derived from fighter escort and formation flying, pursued a policy of daylight raids against specific industrial targets. Urban areas were more susceptible to incendiary bombs than were the individual plants and factories. And while the Eighth Air Force only gradually realized that incendiaries had a part in industrial bombing, the RAF quickly saw the efficacy of the incendiary against larger area urban targets. The Eighth Air Force’s use of aerial incendiaries was effective, but not spectacular, and most of the damage to German cities resulted from RAF operations. This relative lack of success cannot be construed as a criticism of the American air unit, whose mission was different from that of the RAF.
The Incendiary Bombing of Japan
The war in the Pacific was marked by the most spectacular and effective use of the aerial incendiary bomb. After March 1945, General LeMay’s all-out incendiary attacks against the vulnerable Japanese cities brought to a culmination the recognition which the incendiary bomb had gradually been winning throughout the war. It was air power which played a very important part in Japan’s decision to capitulate, and it was the incendiary bomb which helped to make air power such a decisive force.
The use of aerial incendiaries against Japan varied considerably from that against Germany and German occupied Europe. For one thing, air fields for the bombardment of Japanese cities were not immediately available as in the case of the Eighth Air Force, which had English bases well within range of German cities. It was not until the Mariana Islands, located some 1,500 miles south of Tokyo, had been taken that American bombers found themselves within bombing range of the Japanese capital and the other important cities on the island of Honshu. Up till that time, the targets throughout the island chains on the road back, and even in Japanese-held China, were not particularly appropriate for incendiary bombing missions.
Another great difference between the air war against Japan and that against Germany was the extreme vulnerability of the Japanese cities to fire. Although fire destruction could be and was wrought on many German cities, they were less likely targets for the incendiary bomb than those of Japan. Ninety-five percent of German
construction, as noted earlier, was brick and stone, and the roofing material, a very vital consideration in starting fires, usually consisted of tile or slate. In contrast, 80 percent of the construction in Japan made use of wood and paper. There was a nucleus of modern fireproofed buildings in the business areas of most Japanese cities, but, generally speaking, the structures of urban areas were made of very inflammable materials. These areas were so compact, so devoid of fire barriers, that an uncontrolled fire could spread very quickly.
The Twentieth Air Force supervised the incendiary blow against Japan. This unusual organization was activated in Washington on 4 April 1944, with General Henry H. Arnold, Commanding General, AAF, as its commander or “executive agent.” The Joint Chiefs of Staff were to make all major decisions about the deployment, missions, and target objectives of the Twentieth Air Force. Its weapon was the very long range bomber, the B-29, and its two principal subordinate units (the actual operating units) were the XX and XXI Bomber Commands.27
Oddly, the XX Bomber Command saw the light of day and in fact delivered its first bombs against Japanese targets before the activation of the Twentieth Air Force. The first major contingent of the (command left the United States on 5 January 1944 and arrived at New Delhi, India, eight days later. Permanent bases for the XX Bomber Command were in India and the advanced bases were located in the vicinity of Chengtu, in western China. Plagued by logistical difficulties and hindered by the fact that the advanced bases were within range of only the cities of Kyushu, among the Japanese targets, the operations of the command were not particularly effective. In fact, it was soon realized that these missions would be little more than “shakedown” training preparatory to the time that B-29 bases could be constructed in the Mariana Islands.
The summer of 1944 saw the American conquest of the greater part of the Marianas, including the islands of Saipan, Guam, and Tinian. This meant that B-29 bases could be located within range of the important cities of Honshu. Even as the three islands were being mopped up, the XXI Bomber Command began constructing airfields for its
five wings. The first strategic mission was flown from Saipan on 24 November 1944.
From November 1944 until the early days of the following March, the XXI Bomber Command used conventional strategic bombing tactics against the cities of Japan. In Europe the Eighth Air Force had developed the concept of precision bombing and to some it seemed to be the solution for the air war against Japan. With a large percentage of the bomb load consisting of high explosives, planes flew high altitude daylight missions against individual industrial targets. For example, on 14 January 1945 B-29’s dropped ninety-four tons of HE on the Mitsubishi Aircraft Plant in Nagoya with only fair results. That this industrial target was attacked seven more times in a period of several months is some indication of the comparative ineffectiveness of these raids.28 European experience was being translated to Pacific use, and not too successfully.
Precision bombing was not the solution for Japanese targets. The physical construction of Japan’s industrial and urban areas was much more combustible than that of Germany. Japanese cities frequently experienced peacetime conflagrations; German cities did not. Industry and labor in Japan were far more concentrated than in Germany. Moreover, area incendiary attacks against Japan would give its “household” industries, upon whose products the larger plants depended, a tremendous setback.29
In December 1944 General Arnold’s headquarters, aware of the vulnerability to fire of Japanese cities, requested that the XXI Bomber Command mount a full-scale incendiary attack against Nagoya. Brig. Gen. Haywood S. Hansell, commanding general of the air unit and a firm believer in daylight, precision bombing, protested but nevertheless ordered incendiary missions against that city, the first being directed against the Mitsubishi Aircraft Engine Works. Encountering bad weather, the force of forty-eight planes bombed the target using radar and inflicted little damage. Early in January 1945, fifty-seven B-29’s, with an incendiary-fragmentation bomb load, struck urban Nagoya, but smoke from the fires made observation and hence evaluation of the results impossible. For the Japanese, probably the most unfortunate
effect of this rather mediocre mission was the development of an overly optimistic opinion of their inefficient fire-fighting system.30
General LeMay replaced General Hansell on 20 January 1945. At first this move brought little change in the tactics and results of the missions of the XXI Bomber Command. Some success resulted from the high altitude precision bombardment of particular Japanese industries, but this success fell far below the expectations almost everyone had for the VLR bomber, the B-29. In an effort to achieve better results, General LeMay made radical changes in his bombing techniques. First, he planned to send his planes not against individual plants and factories, but against Japan’s combustible cities, filled with home industries as well as with various military installations. Although this plan was itself a departure from the established routine, the courage LeMay needed in making his decision came not from changing targets but from his faith in new methods by which the targets would be attacked. The innovations in tactics all were based on the idea of dropping the most damaging payload on the crowded, inflammable enemy cities.
The planes were to attack at altitudes of from 6,000 to 7,000 feet instead of the usual 20,000 and 30,000, a change partly prompted by the weather encountered over the island of Honshu. At the higher altitude strong winds buffeted the aircraft causing not only an unduly large consumption of gasoline but inflicting punishment on men and planes as well. Moreover, cloud formations over Honshu prevented the visual bombardment of targets on all but a very few occasions. In another change, the planes were to make individual runs against the target instead of attacking in formation. Formation flying was the established practice of the Eighth Air Force, and it provided an all-around defense against attacks by enemy fighter planes. But it also involved rendezvous points for the planes and hence a greater consumption of gasoline. In still another innovation. LeMay ordered the B-29’s to attack under the cover of darkness, a tactic expected to achieve surprise and take advantage of the enemy’s weak defensive weapons, night fighters and radar gun-laying devices. Finally, the aircraft were to be stripped of all armament. The savings in weight resulting from the absence of armament and the lesser demands for gasoline meant that a
greater amount of payload could be carried. And this payload was to consist exclusively of incendiary bombs.31
The XXI Bomber Command first used these tactics on its historic mission No. 40 flown against Tokyo on the night of 9-10 March 1945. The planes carried two types of incendiary bombs, the M47A2 and the M69.32 The Pathfinder units, one squadron of each of the three participating wings, carried the M47s which served not only as aiming points but which also started appliance fires—those fires large enough to be controlled only by special fire-fighting apparatus. The M69s used by the rest of the force started a multitude of small fires that soon joined to form large ones.33 The M47 had been used extensively in Europe, but the M69, because of its poor penetrating power, had proved unsuitable for German targets. This very characteristic made it particularly appropriate for use against the flimsy construction of Japanese buildings.
The ingenious M69, unlike most other American incendiaries, was not based on a European prototype but was strictly an American development. The over-all weight of this hexagonal shaped, light-cased munition was six pounds; its incendiary filling, napalm, weighed three pounds. The bomb, having a terminal velocity of 225 feet per second, was stabilized in flight by cloth streamers rather than by fins. A delay fuze, activated by the impact, ignited an ejection charge which expelled the incendiary material through the tail of the bomb. Thus when the bomb came to rest it functioned like a small mortar; when flat on the floor it could eject flaming napalm as far as 100 feet until it struck an object in its path.34
The first B-29’s left Guam at 1735 on 9 March, and by 2020 the entire attacking force was airborne. Although the planes encountered some bad weather on the way to Tokyo, they identified the coast initial point and target without difficulty. The first bombs landed on Tokyo at 0015 on the following morning. It took but thirty minutes for the
Tokyo, after the incendiary bombing of 9–10 March, 1945
development of fires of conflagration size, and by that time the situation was so far out of hand that efforts to combat the flames were fruitless. The multitude of bombs (1,665 tons were dropped on Tokyo) , the combustible nature of the structures, and the high winds all contributed to the creation of the inferno.
Some people were able to escape through the wide fire lanes, but many others were encircled by the flames and died of suffocation and burns. Those who fled to the canals faced death in the scalding water or were crushed by the terrified mob which crowded in on top of them. This raid alone caused the death of an estimated 83,793 people and almost 41,000 more received injuries. Over one million people lost their homes.
The fire destroyed 15.8 square miles in the center of Tokyo. All buildings in the area were entirely destroyed or seriously damaged.
Although some of the modern, fire-resistant structures were not totally destroyed, the majority of even this type was left as sagging skeletons. Glass, steel bars, and concrete melted in the intense heat; wooden buildings went up in flames before the fire front had reached them. Such was the havoc wrought by the first of the “blitz” raids against the cities of Japan.
The results achieved by the XXI Bomber Command left no doubt as to the validity of the revolutionary tactics of General LeMay. Tokyo had been surprised by both the low altitude and the magnitude of the attack. The command suffered but moderate losses; 14 of the z79 planes over Tokyo failed to return. These losses came not from enemy fighter opposition, which failed to damage a single B-29, but from flak. The combination of bombs used was excellent.
Following the Tokyo raid at about 2-day intervals, Nagoya, Osaka, Kobe, and again Nagoya received the terrible punishment of incendiary bombing. Throughout the rest of the Pacific war a total of sixty-nine Japanese cities were subjected to these “blitz” attacks.35
The Fire Bomb: The Tactical Weapon
Incendiary munitions were useful in tactical air missions—those flown in the combat zone for the purpose of influencing the local tactical situation. Enemy strongholds, motorized vehicles, troop concentrations, and military stores were targets particularly vulnerable to fire. Sometimes tactical aircraft used M47 and M50 bombs against these targets, and occasionally they dropped an M76, but another type of incendiary munition, the fire bomb (often called the napalm or blaze bomb) , proved most effective against tactical targets.
Employment in Europe
A fire bomb was simply a large capacity container filled in the field with napalm gel.36 It began as a field improvisation. Fighter planes carried jettisonable fuel tanks for long missions, and it became customary for the pilots, on the trip homeward, to drop these tanks on targets
Attaching an empty 108-gallon fire bomb tank to the fuselage of a P-47
of opportunity, igniting the gasoline with tracer ammunition. It was only a small step to provide these tanks with igniters more convenient and reliable than tracer ammunition. The CWS devised an igniter from an all-ways fuze and a shortened section of a 2-pound magnesium bomb which was clamped on the side of the gasoline tank. It was soon realized that thickened fuel would provide a more satisfactory fire than ordinary gasoline, so air and chemical officers in Europe began thickening gasoline in spare tanks with oil, or rosin oil and lime, or when they were available, with the approved thickeners, British perspex and American napalm. Because the thickened fuel required a better igniter, chemical officers adapted the white phosphorus grenade for the purpose. One of the most favorable features of the bomb was the ease with which it could be constructed from materials which were relatively abundant, since the spare tanks, often made of process paper, were stocked in quantity. The ratio of filling to the over-all weight of the munition was high. The extreme accuracy with which the fire bomb could be placed on small targets was another major advantage, although this precision
was possible only when the bombs were released from a low altitude, something pilots under heavy antiaircraft attack could not always do.37 An example of the effectiveness of the fire bomb against point targets took place on 25 August 1964 when sixteen fighter planes, carrying twenty-four 165-gallon napalm bombs and eight 500-pound HE bombs, attacked the headquarters of Generalfeldmarschall Guenther von Kluge, German Army Group commander, at Verzy, France. Twenty-two of the napalm tanks made direct hits on the buildings comprising the headquarters; eight houses were completely destroyed.38
Although men were more vulnerable than material to the fire bomb, motorized vehicles, marshaling yards, warehouses, and other combustible buildings made excellent napalm bomb targets. Fighter planes carrying this munition flew frequent missions against the Germans while the latter were attempting to escape encirclement at Falaise. During this period twelve P-38 fighters, each carrying two 165-gallon fire bombs, attacked a concentration of enemy trucks and armor, destroying or damaging an estimated thirty or forty vehicles. At the time of the Ardennes counteroffensive American planes used fire bombs effectively against German motor transportation and armored concentrations in the wooded sections of the area. When fighter planes dropped seventy-two fire bombs on the marshaling yards at St. Quentin, France, 400 of the 500 railway cars in the yards were destroyed.39
The munition was sometimes used in conjunction with artillery or high explosive bombs in attacks against fortified towns or strongpoints consisting of open emplacements and earth and log fortifications. In one approved sequence, these positions first were subjected to artillery fire or high explosive bombing. Then planes dropped fire bombs on the rubble forcing the enemy into the open. Just before the infantry assault, the artillery placed its fire on the exposed enemy troops.40 The fire bomb, however, had little or no effect against heavy fortifications such as the pillboxes of the Siegfried Line. And, reports to the contrary,
the Operational Research Section of the IX Bomber Command found that the fire bomb was not instrumental in the surrender of the fortress of St. Malo on the French coast.41
Use in the Pacific
In the war against Japan, the fire bomb saw use from the mainland of Asia to the many small islands of the Pacific. As in Europe, the munition gave best results when used to produce casualties. Some observers in the Pacific went as far as to say that matériel destruction should be but a secondary mission for the fire bomb and then only if the target were highly combustible. Apart from its casualty potential the fire bomb had definite psychological effect on enemy troops; ground commanders agreed that enemy morale suffered an obvious decrease after a fire bomb attack. The Japanese on Tinian, after experiencing several fire bomb attacks, broke from their positions upon the approach of fighter planes with belly tanks and ran in a direction that was at right angles to the flight of the planes. But whether used against troops or other targets, fire bombs to be effective had to be dropped in adequate numbers. Prisoners of war stated that widely dispersed fire bomb hits had little or no effect on the morale of a unit.42
When used against emplacements the fire bomb performed the additional service of burning off the dense foliage and camouflage which so often surrounded Japanese positions. The Commanding General, 8 1st Infantry Division, stated, “Napalm bombing serves as an excellent means of uncovering hostile strong points in jungle and cave warfare. Unless the enemy is prepared to meet it by special provisions in his caves, this fire will drive him into the open where he can be reached with HE shells.”43
Used in collaboration with regular incendiary and HE bombs, the napalm bomb burned cities and towns in Burma and China whose wooden buildings housed supplies for Japanese operations. For example, the Fourteenth Air Force struck Paoching with M50 and M69 incendiary bombs and demolition and napalm bombs. In this particular
case the results (the destruction of 20 percent of the city) were substandard because of the mud and brick walls of the buildings and because many of the bombs fell on previously burned areas. In Burma, fire bombs alone received credit for the evacuation of one Japanese-held city.44
During the Luzon campaign American air units dropped on the enemy a total of 1,054,200 gallons of napalm-thickened gasoline, of which an estimated 989,000 gallons were effectively placed on targets. The failures were the result of defective igniters and of faulty release mechanisms. While on certain missions there may have been an unusually high percentage of duds (these, likely as not, were ignited by strafing), in the over-all picture the fire bomb performed efficiently.45
The most effective use of the fire bomb took place during the fight for Ipo Dam, north of the city of Manila.46 After the fall of the Philippine capital the Japanese forces withdrew to this area and augmented the natural defensive features of the terrain with a network of trenches and fortified caves. The low supply of water in Manila made the recapture of the dam imperative, and fighter-bombers of the Fifth Air Force supported troops of XI Corps as they attacked to take this important facility. During the initial stage of the operation (3–5 May 1945), 238 planes dropped demolition and fire bombs on the outlying defenses of the dam with good results. The final all-out effort to seize the dam took place on 17 May. On the day before, fighter planes again struck the Ipo defenses, this time with 50,000 gallons of napalm. On the day of the attack 240 fighter-bombers dropped 62,500 gallons of napalm. A Fifth Air Force report described the technique:
Five enemy strong points were selected as target areas, each one consisting of about 3,000,000 square yards. Obviously, in a target of this size, the term saturation bombing is used in a tactical rather than physical sense, meaning that sufficient bomb coverage was provided to negate enemy opposition. To administer the blanket of fire
treatment, 200 to 250 5th AF fighters came in low, wave after wave, four to eight abreast, with air and ground controllers giving target information and regulating traffic. At first, the closely spaced fighters found that smoke from preceding waves obscured the target. The problem was overcome by directing the bombing runs downwind, with each successive wave dropping its bombs on the near side of the bursts from the wave which preceded it. The fighter bombers followed each other at 10- to 15-second intervals. A-20s then came in, showering the area with parafrags and winding up with a thorough strafing.47
Positions in the area which had withstood infantry attacks for almost a week, were taken after only feeble resistance and minimum casualties. Whether these results were entirely due to the use of napalm is not certain. One chemical officer, for example, viewing one of the attacks from the air, concluded that its effect was little more than harassing. But most observers were inclined to place greater emphasis on the effectiveness of the fire bomb, and General Krueger, Sixth Army commander, went so far as to say that these attacks “made possible the early capture of the vital Ipo Dam.”48
All together during World War II the American Army Air Force dropped about 37,000 CWS fire bombs (14,000 tons) on German and Japanese targets. Two-thirds of the bombs and an even higher percentage of the tonnage were used in the Pacific war. No matter where the fire bombs were used reaction to their method of employment seemed to be the same. To insure the best results they had to be dropped in adequate numbers and from altitudes ranging from 50 to 100 feet; the efficiency of a napalm strike was increased when coordinated with HE bombs, artillery fire, or strafing; the most effective targets for the munition were enemy strongholds and troop concentrations, extremely inflammable material, and motorized vehicles.49