White phosphorus

White phosphorus sample

White phosphorus glows when exposed to air

White phosphorus is a material made from a common allotrope of the chemical element phosphorus that is used in smoke, tracer, illumination and incendiary munitions. Other common names include WP, and the slang term "Willie Pete," which is dated from its use in Vietnam, and is still sometimes used in military jargon. As an incendiary weapon, white phosphorus burns fiercely and can set cloth, fuel, ammunition and other combustibles on fire, and cause serious burns or death.

In addition to its offensive capabilities, white phosphorus is also a highly efficient smoke-producing agent, burning quickly and causing an instant bank of smoke. As a result, smoke-producing white phosphorus munitions are very common, particularly as smoke grenades for infantry, loaded in grenade launchers on tanks and other armored vehicles, or as part of the ammunition allotment for artillery or mortars. These create smoke screens to mask movement, position or the origin of fire from the enemy. White phosphorus is used in bombs, artillery, mortars, and short-range missiles which burst into burning flakes of phosphorus upon impact.

History

A USAF Airman inspects 2.75 inch white phosphorus marking rockets in Osan Air Base, Republic of Korea, 1996.

White phosphorus is believed to have been used by Fenian arsonists in the 19th century in the form of a solution in carbon disulfide. When the carbon disulfide evaporated, the phosphorus would burst into flames, and probably also ignite the highly flammable carbon disulfide fumes. This mixture was known as "Fenian fire" and allegedly was used by disgruntled itinerant workers in Australia to cause delayed destruction of shabby sleeping quarters.

In 1916, during an intense ideological struggle over conscription for the First World War, twelve members of the I.W.W., a radical union of workers who opposed conscription, were arrested and convicted for using or plotting to use incendiary materials, including phosphorus. It is believed that eight or nine men in this group, known as the Sydney Twelve, had been framed by the police. Most were released in 1920 after an inquiry.

World War I, the inter-war period and World War II

The British Army introduced the first factory-built WP grenades in late 1916. During World War II, white phosphorus mortar bombs, shells, rockets and grenades were used extensively by American, Commonwealth, and, to a lesser extent, Japanese forces, in both smoke-generating and antipersonnel roles. The British military also used white phosphorus bombs against Kurdish villagers and Al-Habbaniyah in Al-Anbar province during the Great Iraqi Revolution of 1920.

Air burst of a white phosphorus bomb over the USS Alabama during a test exercise conducted by General Billy Mitchell, September 1921.

In the interwar years, the U.S. Army trained using white phosphorus, by artillery shell and air bombardment.

In 1940, when the invasion of Britain seemed imminent, the phosphorus firm of Albright and Wilson suggested that the British government use a material similar to Fenian fire in several expedient incendiary weapons. The only one fielded was the Grenade, No. 76 or Special Incendiary Phosphorus grenade, which consisted of a glass bottle filled with a mixture similar to Fenian fire, plus some latex (see also Molotov cocktail, Greek fire). It came in two versions, one with a red cap intended to be thrown by hand, and a slightly stronger bottle with a green cap, intended to be launched from the Northover projector (a crude 2.5 inch blackpowder grenade launcher). These were improvised anti-tank weapons, hastily fielded in 1940 when the British were awaiting a German invasion after losing the bulk of their modern armaments in France in May 1940. Instructions on each crate of SIP grenades included the observations, among other things:

Store bombs (preferably in cases) in cool places, under water if possible.

Stringent precautions must be taken to avoid cracking bombs during handling.

These weapons were generally regarded as presenting a danger to their own operators and were never deployed in combat.^{[citation needed]}

At the start of the Normandy campaign, 20% of American 81mm mortar rounds were white phosphorus. At least five American Medal of Honor citations mention their recipients using white phosphorus grenades to clear enemy positions, and in the 1944 liberation of Cherbourg alone, a single U.S. mortar battalion, the 87th, fired 11,899 white phosphorus rounds into the city. The U.S. Army and Marines used white phosphorus shells in 107-mm (4.2 inch) mortars. White phosphorus was widely credited by Allied soldiers for breaking up German infantry attacks and creating havoc among enemy troop concentrations during the latter part of the war.

Incendiary bombs were used extensively by the German, British and U.S. air forces against civilian populations and targets of military significance in civilian areas, including London, Hamburg, and Dresden. Late in the war, some of these bombs used white phosphorus (about 1–200 grams) in place of magnesium as the igniter for their flammable mixtures. The use of incendiary weapons against civilians was banned by signatory countries in the 1980 Convention on Certain Conventional Weapons Protocol III. The USA signed Protocols I and II on 24 March 1995 under the Clinton Administration (and the amended article II on 24 May 1999) and later Protocols III, IV, and V, on 21 January 2009 under the Obama Administration.

Later uses

A USAF Security Police Squadron member packs an 81 mm white phosphorus smoke-screen mortar round during weapons training, 1980.

White phosphorus munitions were used extensively in Korea, Vietnam and later by Russian forces in Chechnya.

Smoke-screening properties

Weight-for-weight, phosphorus is the most effective smoke-screening agent known, for two reasons: firstly, it absorbs most of the screening mass from the surrounding atmosphere and secondly, the smoke particles are an aerosol, a mist of liquid droplets which are close to the ideal range of sizes for Mie scattering of visible light. This effect has been likened to three dimensional textured privacy glass—the smoke cloud does not simply obstruct an image, but thoroughly scrambles both visual and infrared radiation, interfering with infra-red optics and weapon-tracking systems, serving as a protection for military forces from guided weapons such as anti-tank missiles.

When phosphorus burns in air, it first forms diphosphorus pentoxide (which exists as tetraphosphorus decoxide except at very high temperatures):

P₄ + 5 O₂ → 2 P₂O₅

Diphosphorus pentoxide is extremely hygroscopic and quickly absorbs even minute traces of moisture to form liquid droplets of phosphoric acid:

2 P₂O₅ + 6 H₂O → 4 H₃PO₄ (also forms polyphosphoric acids such as pyrophosphoric acid, H₄P₂O₇)

Since an atom of phosphorus has an atomic mass of 31 but a molecule of phosphoric acid has a molecular mass of 98, the cloud is already 68% by mass derived from the atmosphere (i.e. 3.2 kilograms of smoke for every kilogram of WP); it may absorb more because phosphoric acid and its variants are hygroscopic. Given time, the droplets will continue to absorb more water, growing larger and more dilute until they reach equilibrium with the local water vapour pressure. In practice, the droplets quickly reach a range of sizes suitable for scattering visible light and then start to dissipate from wind or convection.

Because of the great weight efficiency of white phosphorus smoke, it is particularly suited for applications where weight is highly restricted, such as hand grenades and mortar bombs. An additional advantage for hand smoke grenades—which are more likely to be used in an emergency—is that the WP smoke clouds form in a fraction of a second. Because WP is also pyrophoric, most munitions of this type have a simple burster charge to split open the casing and spray fragments of WP through the air, where they ignite spontaneously and leave a trail of rapidly thickening smoke behind each particle. The appearance of this cloud forming is easily recognised; one sees a shower of burning particles spraying outward, followed closely by distinctive streamers of white smoke, which rapidly coalesce into a fluffy, very pure white cloud (unless illuminated by a coloured light source).

Various disadvantages of white phosphorus are discussed below, but one which is particular to smoke-screening is "pillaring". Because the WP smoke is formed from fairly hot combustion, the gasses in the cloud are hot, and tend to rise. Consequently the smoke screen tends to rise off the ground relatively quickly and form aerial "pillars" of smoke which are of little use for screening. Tactically this may be counteracted by using white phosphorus to get a screen quickly, but then following up with emission type screening agents for a more persistent screen. Some countries have begun using red phosphorus instead. Red phosphorus ("RP") burns cooler than WP and eliminates a few other disadvantages as well, but offers exactly the same weight efficiency. Other approaches include white phosphorus-soaked felt pads (which also burn more slowly, and pose a reduced risk of incendiarism) and PWP, or plasticised white phosphorus.

Effects on people

White phosphorus can cause injuries and even death in three ways: by burning deep into tissue, by being inhaled as a smoke, and by being ingested. Extensive exposure by burning and ingestion is fatal.

Burning

Incandescent particles of WP cast off by a WP weapon's initial explosion can produce extensive, deep second and third degree burns. One reason why this occurs is the tendency of the element to stick to the skin. Phosphorus burns carry a greater risk of mortality than other forms of burns due to the absorption of phosphorus into the body through the burned area, resulting in liver, heart and kidney damage, and in some cases multiple organ failure. These weapons are particularly dangerous to exposed people because white phosphorus continues to burn unless deprived of oxygen or until it is completely consumed. In some cases, burns are limited to areas of exposed skin because the smaller WP particles do not burn completely through personal clothing before being consumed.

Smoke inhalation

Burning white phosphorus produces a hot, dense, white smoke consisting mostly of phosphorus pentoxide. Exposure to heavy smoke concentrations of any kind for an extended period (particularly if near the source of emission) does have the potential to cause illness or even death. White phosphorus smoke irritates the eyes, mucous membranes of the nose, and respiratory tract in moderate concentrations, while higher concentrations may produce severe burns. However, no casualties have been recorded from the effects of white phosphorus smoke alone in combat operations and there are no confirmed deaths resulting from exposure to phosphorus smoke.^{[citation needed]} The Agency for Toxic Substances and Disease Registry has set an acute inhalation Minimum Risk Level (MRL) for white phosphorus smoke of 0.02 mg/m³, the same as fuel oil fumes. By contrast, the chemical weapon mustard gas is 30 times more potent: 0.0007 mg/m³.

Oral ingestion

The accepted lethal dose when white phosphorus is ingested orally is 1 mg per kg of body weight, although the ingestion of as little as 15 mg has resulted in death. It may also cause liver, heart or kidney damage. There are reports of individuals with a history of oral ingestion who have passed phosphorus-laden stool ("smoking stool syndrome").

Arms control status and military regulations

There are multiple international laws that could be seen to regulate white phosphorus use. Article 1 of Protocol III of the Convention on Certain Conventional Weapons defines an incendiary weapon as 'any weapon or munition which is primarily designed to set fire to objects or to cause burn injury to persons through the action of flame, heat, or combination thereof, produced by a chemical reaction of a substance delivered on the target'. The same protocol prohibits the use of said incendiary weapons against civilians (already forbidden by the Geneva Conventions) or in civilian areas.

However, the use against military targets outside civilian areas is not explicitly banned by any treaty. There is a debate on whether white phosphorus should be considered a chemical weapon and thus be outlawed by the Chemical Weapons Convention (CWC) which went into effect in April 1997. The convention is meant to prohibit weapons that are "dependent on the use of the toxic properties of chemicals as a method of warfare" (Article II, Definitions, 9, "Purposes not Prohibited" c.).

The convention defines a "toxic chemical" as a chemical "which through its chemical action on life processes can cause death, temporary incapacitation or permanent harm to humans or animals" (CWC, II). An annex lists chemicals that fall under this definition and WP is not listed in the Schedules of chemical weapons or precursors.

In an 2005 interview with RAI, Peter Kaiser, spokesman for the Organisation for the Prohibition of Chemical Weapons (an organization overseeing the CWC and reporting directly to the UN General Assembly), questioned whether the weapon should fall under the convention's provisions:

No it's not forbidden by the CWC if it is used within the context of a military application which does not require or does not intend to use the toxic properties of white phosphorus. White phosphorus is normally used to produce smoke, to camouflage movement.

If that is the purpose for which the white phosphorus is used, then that is considered under the convention legitimate use.

If on the other hand the toxic properties of white phosphorus are specifically intended to be used as a weapon, that of course is prohibited, because the way the convention is structured or the way it is in fact applied, any chemicals used against humans or animals that cause harm or death through the toxic properties of the chemical are considered chemical weapons".

Kaiser was a staff spokesman for the Organisation for the Prohibition of Chemical Weapons. The OPCW, using member votes, creates Schedules of chemical weapons or dual-use chemicals of concern and white phosphorus is not in any of these schedules.

The Convention on Certain Conventional Weapons, not the Chemical Weapons Convention, goes on, in its Protocol III, to prohibit the use of all air-delivered incendiary weapons against civilian populations, or for indiscriminate incendiary attacks against military forces co-located with civilians. However, that protocol also specifically excludes weapons whose incendiary effects are secondary, such as smoke grenades. This has often been read as excluding white phosphorus munitions from this protocol, as well. Several countries, most notably Israel, are not signatories to Protocol III.

The legal position however, is not the only consideration in any war. For instance, concerning the U.S. use of white phosphorus in Iraq, the British Liberal Democrat foreign affairs spokesman Sir Menzies Campbell, said

"The use of this weapon may technically have been legal, but its effects are such that it will hand a propaganda victory to the insurgency. The denial of use followed by the admission will simply convince the doubters that there was something to hide".

Military regulations

Within the US Army, there appears to be conflicting advice on the use of WP against humans. According to the field manual on the Rule of Land Warfare, "The use of weapons which employ fire, such as tracer ammunition, flamethrowers, napalm and other incendiary agents, against targets requiring their use is not violative of international law." However, the 11-year-old ST 100-3 Battle Book, a student text published by the US Command and General Staff College at Fort Leavenworth states that "It is against the law of land warfare to employ WP against personnel targets." At the same time, other field manuals discuss the use of white phosphorus against personnel.

Though white phosphorus is still used in modern armed conflict, it is regulated by international humanitarian law, or the law of war.

External links

• The Legality of the Use of White Phosphorus by the United States Military During the 2004 Fallujah Assaults (Roman Reyhani)
• Globalsecurity.org on WP (including use during the Battle of Fallujah and during the December 1994 battle for Grozny during the First Chechen War)