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  • History Friday: Napalm as a Weapon

    Posted by Trent Telenko on November 8th, 2013 (All posts by )

    One of the focal points in my writing these History Friday columns has been trying to answer the question “How would the American military have fought the Imperial Japanese in November 1945 if the A-bomb failed?” Today’s column returns to that theme by examining one of many “reality lives in the detail” changes in material, training and doctrine that the US Army was making for the invasion of Japan. This column’s focus is on the use of napalm as a weapon. In reading about napalm as a weapon in World War 2, you see the following (from the Global Security web site) standard narrative explanation and not much more —

    Napalm was developed at Harvard University in 1942-43 by a team of chemists led by chemistry professor Louis F. Fieser, who was best known for his research at Harvard University in organic chemistry which led to the synthesis of the hormone cortisone. Napalm was formulated for use in bombs and flame throwers by mixing a powdered aluminium soap of naphthalene with palmitate (a 16-carbon saturated fatty acid) — also known as naphthenic and palmitic acids — hence napalm [another story suggests that the term napalm derives from a recipe of naphtha and palm oil]. Naphthenic acids are corrosives found in crude oil; palmitic acids are fatty acids that occur naturally in coconut oil. On their own, naphthalene and palmitate are relatively harmless substances.
    The aluminum soap of naphthenic and palmitic acids turns gasoline into a sticky syrup that carries further from projectors and burns more slowly but at a higher temperature. Mixing the aluminum soap powder with gasoline produced a brownish sticky syrup that burned more slowly than raw gasoline, and hence was much more effective at igniting a target. Compared to previous incendiary weapons, napalm spread further, stuck to the target, burned longer, and was safer to its dispenser because it was dropped and detonated far below the airplane. It was also cheap to manufacture.

    There is a lot more to napalm than just that, and you can’t really understand combat after action reports, the detailed reality, of the WW2 Pacific Theater without being aware of the capabilities and limitations of napalm as a weapon. The following list is from my own research over the last few years on the subject of tank-mounted mechanized flamethrowers that were in my last column.

    1) Napalm flame fuel was a “Non-Newtonian Fluid” as compared “Newtonian fluids” like water and gasoline. Everyday examples of “Non-Newtonian Fluids” include corn starch and milk gravy, alcohol hand sanitizer, hair gel, and ketchup. This meant that Napalm mixtures acted somewhat like a semi-solid glue when at rest and like fluid under pressure or when aerosolized. For example, if one takes a bottle full of water and a bottle of ketchup, then try to shoot fluids from both through a potted plant to a board behind it. The water will push the plant aside and predominantly move through to the board. The ketchup will stick to the plant, and the resultant flow will have far less will reach the board behind it, let alone hit where it was intended.

    This had huge implications in 1943-1944 when fighting in triple canopy jungle, dense undergrowth or in tall Kunai Grass. The South Pacific was noted for all of the above. In thick foliage napalm mixtures fired from flamethrowers stuck to plants rather than pushed past them like a Newtonian fluid. Quite literally, plant vegetation concealment _WAS COVER_ for firing apertures in bunkers of any sort. You also could not do an arcing overhead stream for fear of the plants so disrupting the flow that you would hit some of your own troops.

    New Georgia thin flame fuel attack -- from 'Portable flame thrower operations in World War II '

    New Georgia Flamethrower attack using thin flame fuel with little or no napalm — Source: ‘Chemical Corps Monograph No. 4 Portable Flame Thrower Operations in World War II’

    2) Napalm was a very chemically unstable compound. There were lots of trace metals, water, alcohol and a number of anti-knock chemicals in gasoline that broke down WW2 Napalm gels back into a thin gasoline. Modern EPA compliant anti-pollution gasoline-alcohol blends, for example, could not make Napalm gels with WW2 Napalm soaps. Such thin fluids had half the range of thickened fluids in flame throwers – 10 yards vs. 20 yards in a portable flamethrower and 40 versus 80(+) yards with a mechanized flamethrower — and delivered only 10% of the fuel heat on the target as compared to 80% to 90% with napalm thickened flame fuel. It wasn’t until just before Operation Olympic in July 1945 that Col Unmacht’s Hawaii flamethrower group developed a silica additive for napalm flame fuel to stabilize the compound for weeks and months long storage without thick-to-thin fuel breakdown. This was going to be debuted with the portable flamethrowers of the 5th Marine and 98th Infantry divisions shipping from Hawaii and all the Hawaii built flame tanks with Marine and Army units.

    Mech Flame Throwers E4-5 (1944) firing thin and Napalm thickened fuel

    Mechanized Flame Throwers E4-5 (1944) firing thin (Top) and Napalm thickened (Bottom) flame fuel. Source: War Dept. TC “TACTICAL USE OF MECHANIZED FLAME THROWERS E5R1-5 AND E4-5,” MAY 1944

    3) The napalm soap oxidized rapidly in air and was very liable to absorb water from humid climates. Once napalm absorbed that water, it floated like soap scum on top of gasoline rather than making thickened flame fuel. This required the development of water proof packaging for the shipment of Napalm additives and consistent additive process recipes for desired flame fuel characteristics. While Napalm was available starting in 1942, Napalm first became available for combat during the latter part of 1943 due to the lag in developing a proper water vapor proof packaging for soldier-proof shipment.

    Packaging of Napalm Thickener for Overseas Shipment -- Source: Chemical Warfare Board Proj. 667, June 5, 1945

    Packaging of Napalm Thickener for Overseas Shipment — Source: Chemical Warfare Board Proj. 667, June 5, 1945

    4) How the napalm was ground was extremely important in order to get “fast setting” (one hour or less) or “slow setting” (12 hours to a day) napalm flame fuel for the proper military application. Most portable and all US Navy fire bomb Napalm was of the finely ground “fast setting” type. The US Navy carriers did not keep napalm fire bombs in storage; they mixed them in fuel tanks on the aircraft during the run up to a strike. Mechanized flame thrower napalm had to be slower setting to get a uniform distribution through the gasoline. This worked best with a coarser ground napalm inside a mechanized mixer with screens on the incoming Napalm and Gasoline to get uniform napalm particles and to keep out water, respectively.

    5) You could not use galvanized steel containers with Napalm in mechanized flame throwers or 55 gallon steel drums for long term storage because WW2 era Napalm gel broke down back to gasoline in them. It was discovered after the war that brass had the same effect, and many of the flame throwers in WW2 had brass fittings.

    6) All of the air pressurized flame throwers the American military used in WW2 lacked both an air dryer and a wet tank between the air compressor and the air pressurization tanks that pushed out napalm fuel. Such systems are used on modern military trucks design with central tire inflation system and air brakes to keep water and other crude in the air from getting into and contaminating air tanks, thus blocking brake lines or obstructing tire air manifolds. Corrosion products from the unprotected air tanks would get into the rubber lines and seals and make the flame gun of both portable and mechanized flamethrowers unreliable without constant monitoring and maintenance. This undiscovered design flaw was hugely important and explains many reliability issues that WW2 portable flamethrowers, the degrading performance of the USN Mark 1 mechanized flame thrower had at Peleliu and the reliability issues of the E4-5 auxiliary mechanized flame throwers had throughout its years of service in Europe and the Pacific.

    7) The combination of the lack of air treatment, brass fittings, and corrosion prone steel flame thrower pressurized air & Napalm containers will make any such flame thrower very unreliable without trained maintenance units and lots of pre-packaged spares. Neither of which happened at any point in during WW2. A “flaming datum” for the problem was the fact that during preparation for the Okinawa campaign, the 27th infantry Division found 27 of its 90 newly issued portable flame throwers were defective in testing before combat! This maintenance problem was finally solved in Sixth Army in the run up to Operation Olympic by attaching a chemical service platoon to each division and designating the battalion and regimental gas officers as flame thrower officers. The battalion gas corporal was also required to be a qualified flame thrower technician. This was a key point of the 6th Army reequipment campaign in the “81st ID Operations Report, Palau Islands to New Caledonia to Leyte P.I. to Japan 5 Jan 1945 to 10 Jan 1946” in my “History Friday: 81st ID’s Peleliu Lessons for MacArthur’s Invasion of Japan” column.

    8) Napalm had a reputation earned on Okinawa of being an exploding fuel. This reputation that caused tank battalions on Okinawa to remove their auxiliary mechanized flame throwers from their tanks. This reputation for napalm happened to be untrue. In fact, napalm behaved as follows —

    a. Napalm gel, especially in concentrations over 5%-to-6% by weight of concentration used in main armament mechanized flame throwers were hard to ignite reliably without the use of a secondary fuel like gasoline coating the flame rod shot. In fact, a full tank of high Napalm concentration gel highly pressurized by air can be shot by a .50 caliber machine gun tracer bullet without exploding.
    b. Empty Napalm tanks, or air pressurized napalm tanks with broken down fuel do explode. As none of the auxiliary flame thowers had any maintenance whatso ever from their installation and first fueling before they landed on Okinawa. It was all but guarenteed that every tank of flame fuel was air pressurized gasoline as American tanks were struck by Japanese anti-tank guns on Okinawa. The Chemical Warfare Service investigations did not confirm exploding fuel, as the napam tanks showed hole and not explosions. The same could not be said of the pressurized _AIR TANKS_.
    c. These facts the CWS told US Army tank operators were not validated until experiments by the Canadians at their Suffield, Alberta experimental station in 1953. The Canadians were trying to prove to both the British & American Armies that they should use inert gases and not air in mechanized flame vehicles.

    9) Post-WW2 Chemical Warfare Service testing showed that Napalm did not kill by “pulling all the oxygen out of the air.” People can breathe atmosphere that fires cannot burn in. Napalm suffocated via carbon monoxide and other combustion products poisoning the air or by scalding lung tissue with superheated air. Napalm causes atmospheres of up to 20% carbon monoxide by volume. The high temperatures from Napalm also caused “hyper thermic shock” that stopped the hearts of its targets. Hence reports of Japanese soldiers dying from Napalm without burns, which combat soldiers reported as the “pulled all the oxygen out of the air” myth.

    10) Napalm concentrations for flame fuel varied by weapon. Aircraft fuel tank flame bombs had to be much thicker, between 12% and 15% by weight in gasoline, to be effective in sticking to ground targets. Portable flame thrower fuels were 3%- 4.5% by weight napalm additive to fuel. Mechanized flame throwers napalm fuel mixture percentages depended upon the ignition source. Direct electric spark ignition mechanized flame throwers like the E4-5 required 5.5% or less napalm by weight. The Hawaii flame tanks and the E7-7 Stuart flame tanks used gasoline secondary fuel and could use 8% to 10% by weight napalm fuel mixtures.

    None of the above was known at the time. Most of it had to be learned by doing, learned by dying. This one of may places where “Reality lives in the unexamined details.” History details that you now know for your future reading. When it came time for the invasion of Japan, American napalm flame weapons were set to be far more effective than any the japanese military had previously faced.

    Notes and Sources:

    “DEVELOPMENT OF FLAME THROWERS, SERVICE UNITS, AND THICKENED FUELS BY STANDARD OIL COMPANY,” National Defense Research Committee Division 11 of the Office of Scientific Research and Development, OSRD REPORT No. 6376, COPY 21, October 31, 1945


    LT COL LEONARD L. McKINNEY, CML C-RES., CHEMICAL CORPS HISTORICAL STUDIES No. 4 “PORTABLE FLAME THROWER OPERATIONS IN WORLD WAR II” Historical Office Office of the Chief, Chemical Corps, 1 December 1949 Pages 1 – 25


    “Report of Activities of the Technical Division During World War II”, Army Service Forces, Office of the chief, Chemical Warfare Service, Washington, D.C., 1 January 1947 — CHAPTER XVII – FLAME THROWERS pages 139 – 148 Passim

    Herman s. Seelig, Captain, C. W. S., “MISCELLANEOUS STUDIES ON THE STABILITY OF NAPALM SOAPS GELS AND NAPALM GELS,” M.1.T.-M.R. NO. 206, Project: A8.7, Chemical Warfare Service Development Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts, Oct 1945



    War Department Training Circular “TACTICAL USE OF MECHANIZED FLAME THROWERS E5R1-5 AND E4-5,” MAY 1944


    2 Responses to “History Friday: Napalm as a Weapon”

    1. Gringo Says:

      This whole post just burns me up.

    2. Joe Wooten Says:

      Hey Gringo, whay are you flaming Trent????

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