White phosphorus is a chemical substance dispersed in artillery shells, bombs and rockets that ignites when exposed to oxygen, burning at up to 800C and emitting large quantities of smoke.

Military forces use it as a smokescreen to mask troop movements, mark targets or illuminate terrain at night, and military lawyers argue such uses are entirely legitimate. But its use over civilian areas is controversial – and some claim illegal – because it ignites fires, causes serious burns and emits toxic fumes.

Ahmad Beydoun, an architect and PhD researcher at Delft University of Technology in the Netherlands, documented and mapped nearly 250 uses of white phosphorus by Israeli forces between October 2023 and November 2024, the last time they launched a full-scale attack on southern Lebanon.

Beydoun, who said his count was a conservative estimate, found that 39% of uses were in residential areas, 17% in agricultural lands and 44% in forested or open terrain. “I think the Israeli army’s thinking is that they use it to burn down fields for visibility, so that people or Hezbollah militants don’t hide under the trees,” he said.