“A very bad odour and massive cloud covered the town so that we were not able to see beyond five or six metres in front of us…Cars caught fire. Land areas were also burnt down. Until today, you find remnants – the size of a fist – that reignite when exposed to air.”

This description, given by Abdullah al-Ghrayyeb, mayor of Dhayra, to Amnesty International, was used as evidence of white phosphorus being used by the Israeli military in an attack on the town in southern Lebanon in October 2023. But what is white phosphorus and what is its legal status as a weapon of war?

What is white phosphorus?

White phosphorus is described by the World Health Organization (WHO) as a “chemical waxy solid substance typically appearing yellowish or colourless,” with an odor that some have described as “resembling garlic.” It instantly ignites on contact with oxygen and, once ignited, is very difficult to extinguish and “sticks to surfaces like skin and clothing.” It is extremely harmful to humans and causes severe burns, “penetrating even through bone.” It brings about severe respiratory problems due to the “phosphoric acids and phosphine” present in the substance. It also carries the risk of re-igniting, which means that medical staff can become secondary victims. Exposure to white phosphorus often has a long-term impact on the health of those affected.

According to the WHO, white phosphorus is used by militaries to “illuminate battlefields, to generate a smokescreen and as an incendiary.” The gaseous spread of white phosphorus means that it covers large areas. It can have a disastrous, indiscriminate effect in densely populated regions, posing a greater threat to civilians than other weapons of comparable explosive power. When they are used as weapons, white phosphorus munitions are classified as incendiary weapons.

What are incendiary weapons and what is their status under international law?

Incendiary weapons are weapons or munitions that have been made to start fires or cause burns and respiratory injuries. They use heat and flames resulting from a chemical reaction. In the case of white phosphorus, that reaction occurs when the substance is exposed to oxygen. Incendiary weapons are not explicitly banned under international law but there are certain restrictions on their use.

Napalm is a well-known example of an incendiary weapon. Indeed, many of the regulations surrounding incendiary weapons came about as a result of the use of the substance in the Vietnam War. The UN General Assembly in 1972 stated that napalm bombing was “among the methods and means that erode human rights.” They further said that the “massive spread of fire through incendiary weapons is largely indiscriminate in its effects on military and civilian targets” and that they deplored “the use of napalm and other incendiary weapons in all armed conflicts.”

A decade later, the Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons Which May Be Deemed to Be Excessively Injurious or to Have Indiscriminate Effects (CCW) was adopted by the UN. In particular, Protocol III on Prohibitions or Restrictions on the Use of Incendiary Weapons was designed to protect civilians and civilian objects from weapons of this kind by prohibiting their use in “concentrations of civilians.” However, while the protocol prohibits the use of air-drop incendiary weapons, it does not limit all use of ground-launched incendiary weapons. It also defines incendiary weapons as those “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.” This means that white phosphorus used primarily as a “smokescreen” could be excluded, even though its effects are similar.

Where are white phosphorus and other incendiary weapons used?

HRW has documented the use of incendiary weapons in Afghanistan, Gaza, Iraq, Syria, Ukraine, and Yemen, asserting that, since 1980, “incendiary weapons have reportedly been used in at least 16 conflicts in 13 countries on three continents.” Their report, from 2017, states that “multipurpose and ground-launched incendiary weapons, which fall within Protocol III’s loopholes, have become fixtures of contemporary armed conflict.”

In October 2023, Amnesty International released evidence of Israel’s use of white phosphorus in southern Lebanon, describing the use as “indiscriminate” and reporting that the munition injured at least nine civilians and damaged civilian objects. Amnesty called for the October 16, 2023 white phosphorus attack on Dhayra to be investigated as a war crime. Aya Majzoub, the deputy regional director for the Middle East and North Africa at Amnesty International said:

It is beyond horrific that the Israeli army has indiscriminately used white phosphorous in violation of international humanitarian law. The unlawful use of white phosphorus in Lebanon in the town of Dhayra on 16 October has seriously endangered the lives of civilians, many of whom were hospitalized and displaced, and whose homes and cars caught fire.

More recently, in June 2024, HRW said that Israel’s extensive use of white phosphorus in southern Lebanon was “putting civilians at grave risk and contributing to civilian displacement.” In October 2024, the Lebanese state-run news agency accused Israel of using white phosphorus bombs in a recent strike that killed at least seven health workers in an apartment building in Beirut.

Similarly, Ukraine has accused Russia of using white phosphorus in several attacks. At the start of the war, Ukranian President Volodymyr Zelensky claimed in a speech to the European Council in March 2022, that “Russian troops are using phosphorus bombs…” In May 2023, the besieged city of Bakhmut, Ukraine appeared to be the target of a white phosphorus attack. Video footage appeared to show the substance falling in an area west of the city, near a children’s hospital. Senior Pentagon officials have recommended giving white phosphorus shells to Ukraine, with the White House repeatedly rejecting the call.

White phosphorus is undoubtedly a risk to civilians and civilian objects due to its indiscriminate nature and the terrifying extent of the harm it inflicts. Organizations such as Human Rights Watch (HRW) have called on countries to tighten Protocol III and the regulations and prohibit the use of all incendiary weapons in concentrations of civilians. However, it remains uncertain whether further regulation will be forthcoming.