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Since the beginning of Israel’s ground offensive in Gaza on January 3, 2009, there have been numerous media reports about the possible use by the Israel Defense Forces (IDF) of white phosphorus (WP), a chemical substance used in military ordnance that has several tactical uses. The IDF has told Human Rights Watch and reporters that it is not using WP in Gaza. On January 7, an IDF spokesman told CNN, “I can tell you with certainty that white phosphorus is absolutely not being used.”

Human Rights Watch believes the IDF is using WP in Gaza. On January 9, Human Rights Watch researchers on a ridge overlooking Gaza from the northwest observed multiple air-bursts of artillery-fired WP that appeared to be over the Gaza City/Jabaliya area. In addition, Human Rights Watch has analyzed photographs taken by the media on the Israel-Gaza border showing Israeli artillery units handling fused WP artillery shells, as well as video of air bursts over Gaza followed by tendrils of smoke and flame that are highly indicative of WP use.

Israel appears to be using WP as an “obscurant” (a chemical used to hide military operations), a permissible use in principle under international humanitarian law (the laws of war). However, WP also has a significant, incidental, incendiary effect that can severely burn people and set structures, fields, and other civilian objects in the vicinity on fire. The potential for harm to civilians is magnified by Gaza’s high population density, among the highest in the world.

Human Rights Watch believes that the use of WP in densely populated areas of Gaza violates the requirement under international humanitarian law to take all feasible precautions to avoid civilian injury and loss of life. This concern is amplified given the technique evidenced in media photographs and viewed by Human Rights Watch researchers on January 9 of air-bursting WP projectiles, which spreads the burning wafers over a wider area, thereby increasing the likelihood of civilian casualties and damage to civilian objects.

What is White Phosphorous?

White phosphorous (WP) is a chemical substance dispersed in artillery shells, bombs, and rockets, used primarily to obscure military operations on the ground. It is not considered a chemical weapon and is not banned per se. WP ignites and burns on contact with oxygen and creates a smokescreen at night or during the day to mask the visual movement of troops. It also interferes with infra-red optics and weapon-tracking systems, thus protecting military forces from guided weapons such as anti-tank missiles. When WP comes into contact with people or objects, though, it creates an intense and persistent burn. It can also be used as a weapon against military targets (see below).

How is WP used?

WP can be air-burst or ground-burst. It emits a distinct “garlic” smell. When air-burst, it covers a larger area than ground-burst and is useful to mask large troop movements. However, this spreads the incendiary effect over a wider area and in densely populated areas, as in much of Gaza, increases the exposure of civilians. When the weapon is ground-burst, the endangered area is more concentrated and the smokescreen remains for longer. The cloud from WP is dependent on atmospheric conditions, so it is impossible to generalize how long it will remain in the air.

WP can also be used as a weapon. US forces used WP during the second battle of Fallujah in Iraq in 2004 to “smoke out” concealed combatants, who were then attacked.

Why is WP controversial?

WP burns anything it touches. When air-burst as an obscurant, it can fall over an area about the size of a football field, about the same area affected by a cluster bomb. Those below may receive horrific skin burns, and it can set structures, fields, and other objects on fire. Using WP against military targets in densely populated areas would also raise concerns where the weapon could not be directed at a specific military target and thus would be indiscriminate in its impact, in violation of the laws of war. Humanitarian law also places restrictions on the use of incendiary weapons like WP against military personnel when other weapons are available.

What is the status of WP under international law?

WP used as weapons are considered incendiaries. Incendiary weapons are not prohibited under the laws of war. However, the use of WP against military targets is regulated under Protocol III of the Convention on Conventional Weapons (CCW). Although Israel is not party to this treaty, customary laws of war prohibit the anti-personnel use of incendiary weapons so long as weapons less likely to cause unnecessary suffering are available.

A 1998 Israeli military manual states: “Incendiary arms are not banned. Nevertheless, because of their wide range of cover, this protocol of the CCW is meant to protect civilians and forbids making a population center a target for an incendiary weapon attack. Furthermore, it is forbidden to attack a military objective situated within a population center employing incendiary weapons. The protocol does not ban the use of these arms during combat (for instance, in flushing out bunkers).”

Is Israel’s use of WP compliant with international law?ç

WP is not an illegal obscurant or weapon. However, Israel’s use of WP as an obscurant in densely populated areas of Gaza violates the obligation to take all feasible precautions to minimize harm to the civilian population during military operations. Human Rights Watch urges Israel immediately to stop using WP in densely populated areas. Human Rights Watch will seek to investigate this matter further.

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