White Phosphorus in Southern Lebanon: What the Incendiary Weapon Does and Why Its Use Is Contested

White phosphorus has returned to the center of international attention amid Israel's ongoing military campaign in southern Lebanon, where the incendiary substance has been deployed in populated areas and against agricultural land. An explainer produced by Al Jazeera, presented by correspondent Reem Takieddine, examines what the chemical actually does to the human body and the environment, how it has been used in Lebanon, and why international law places strict limits on its employment near civilians.

At its most basic, white phosphorus is a waxy, yellowish or colorless solid that ignites spontaneously when exposed to oxygen in the air. Once alight, it burns at extraordinarily high temperatures and is notoriously difficult to extinguish. Because the substance continues to react with oxygen, a single particle can reignite after it appears to have been smothered, meaning that wounds associated with it can re-open and burn anew even after initial treatment.

The weapon's destructive capacity extends well beyond direct fire. White phosphorus generates intense heat capable of burning flesh down to the bone, and it produces a dense, toxic smoke that can damage the respiratory system when inhaled. Victims who survive exposure frequently suffer deep thermal injuries that are slow to heal and highly prone to infection, and particles lodged in tissue may continue to smolder for hours or days.

Those characteristics explain why the substance is classified as an incendiary weapon rather than a conventional explosive. It does not rely on blast fragmentation to cause casualties; instead, it inflicts harm through combustion and chemical toxicity. Its effects are therefore felt not only by those in the immediate impact zone but also by people who encounter residual particles later, including medical personnel treating the wounded.

According to the Al Jazeera explainer, Israel has used white phosphorus in southern Lebanon, where its impact has fallen on civilian populations and on farmland. Agricultural damage is a particular concern in a region where many communities depend on seasonal crops for their livelihoods. Contamination of soil and crops can persist long after active hostilities end, compounding the economic harm inflicted on communities already displaced by fighting.

The use of such munitions in populated areas is restricted under international humanitarian law. The core obligation is the principle of distinction, which requires parties to a conflict to differentiate between military objectives and civilians, and the principle of proportionality, which prohibits attacks expected to cause civilian harm excessive in relation to the military advantage anticipated. Because white phosphorus disperses over a wide area and cannot be precisely directed once ignited, its deployment near residential neighborhoods raises serious legal questions.

International law does not ban white phosphorus outright. It is permitted for certain purposes, such as producing smoke screens to obscure troop movements or to mark targets, and some armed forces treat it as a legitimate obscurant. The controversy arises when the substance is fired into areas where civilians live, work, or farm, where its indiscriminate reach makes compliance with distinction and proportionality extremely difficult to guarantee.

Human rights organizations and legal experts have repeatedly argued that using air-burst white phosphorus over populated areas amounts to an indiscriminate attack, and in some cases they have characterized such use as a war crime. The debate often turns on intent and on the specific delivery method: ground-level smoke employment differs substantially from exploding shells that scatter burning fragments across a wide radius.

For civilians in southern Lebanon, the consequences are both immediate and long-term. The Al Jazeera report highlights the danger of severe burns, the risk of repeated ignition of wounds, the inhalation of toxic fumes, and the destruction of agricultural land. Beyond physical injury, the presence of such weapons drives displacement, undermines food security, and leaves psychological trauma that can endure well after the fighting subsides.

Medical professionals face particular challenges in treating exposure. Standard burn care is complicated by the chemical nature of the injury, and embedded phosphorus particles must be kept submerged or smothered to prevent re-ignition. In conflict zones where hospitals are overwhelmed or damaged, accessing the specialized treatment required for these injuries is often impossible, worsening outcomes for victims.

The renewed scrutiny of white phosphorus in Lebanon also fits a broader pattern of concern about the weapon's use in the region. Allegations of its deployment have surfaced in previous conflicts, prompting investigations by human rights groups and repeated calls for greater transparency and accountability from the parties involved. Each new report adds pressure on international bodies to document incidents and assess whether the laws of war were respected.

From a legal standpoint, accountability remains difficult to achieve. Establishing that a particular munition was used, identifying the unit responsible, and proving that commanders knew or should have known of the civilian risk requires evidence that is hard to gather amid active fighting. International courts and investigative mechanisms depend on documentation, witness testimony, and forensic analysis, all of which take time and face serious access constraints.

The strategic logic behind employing white phosphorus is also contested. Militaries argue it can be effective for screening maneuvers, denying visibility, and marking targets. Critics counter that when it is fired into civilian areas, the resulting harm is foreseeable and disproportionate, and that the availability of alternative obscurants weakens any justification for using it in densely populated terrain.

For the communities of southern Lebanon, the immediate priority is protection and relief, while the longer-term question is whether those responsible for any unlawful use will be held to account. The Al Jazeera explainer serves as a reminder that the debate over white phosphorus is not abstract: it concerns a weapon whose burns reignite, whose smoke poisons the air, and whose residue lingers in the soil that families depend on for their next harvest.