Daniel sent us this one — and it's a heavy one. He says we were talking earlier about the weird history of gas masks in Israel, why every apartment has one as a relic, and that got us into nerve agents and chemical weapons. Now he wants to zero in on one weapon that's especially controversial: white phosphorus. He's asking which militaries have been documented using it, what international safeguards are supposed to ban it, and what makes it so devastating in civilian areas. And then there's a taxonomy question — where does white phosphorus fit within the CBRN division we talked about in the nerve agent episode? Because it doesn't sit neatly in any one box.
It doesn't. And that taxonomic weirdness is actually central to why the legal framework around it is such a mess. White phosphorus is this strange chimera — it's an incendiary, it's a smoke-producing agent, it's technically not a chemical weapon under the Chemical Weapons Convention, and yet it produces effects that look an awful lot like chemical burns. So you've got something that falls between three or four different legal categories, and militaries exploit every one of those gaps.
The Swiss Army knife of horrible things.
That's uncomfortably accurate. So let's start with what it actually is. White phosphorus is a waxy solid that ignites spontaneously when it hits oxygen — at about thirty degrees Celsius, so basically room temperature on a warm day. When it burns, it hits around eight hundred to fifteen hundred degrees Celsius. It sticks to surfaces. It keeps burning as long as it's exposed to air. And the smoke it produces is intensely hygroscopic — it pulls moisture out of the air, out of your eyes, out of your lungs, forming phosphoric acid.
You're getting burned and chemically corroded at the same time.
And the burns are deep — often down to the bone — because the phosphorus particles embed themselves in tissue and keep reigniting every time the wound is exposed to air during treatment. There are documented cases from conflict zones where medical staff would debride a wound, expose it to air, and watch it reignite on the operating table.
That's a detail I wish I didn't know now.
Welcome to this episode. So the physical mechanism here matters for the legal question. White phosphorus is primarily classified as an incendiary weapon, not a chemical weapon. The Chemical Weapons Convention, which came into force in nineteen ninety-seven, explicitly excludes munitions where the toxic effects are incidental to a primary intended purpose — and the military argument has always been that white phosphorus is used for smoke-screening, for illumination, for marking targets, and the incendiary effects are secondary.
Which is the legal equivalent of "I wasn't trying to burn people, I was just trying to light up the battlefield.
That argument has been tested repeatedly. The key legal instrument is Protocol Three of the Convention on Certain Conventional Weapons — the CCW. It prohibits the use of air-dropped incendiary weapons in concentrations of civilians, but here's the gap: it doesn't cover ground-launched incendiaries in the same way, and it doesn't cover weapons where the incendiary effect is not the primary design purpose. The United States, by the way, is not a party to Protocol Three.
Of course it isn't.
Israel isn't either. Neither is Russia. Neither is China. The protocol has about a hundred and twenty-five parties, but several of the major military powers have simply never signed on.
You've got the countries most likely to use these things opting out of the rules that govern them. That's not a loophole, that's an architectural feature.
It's the multilateral arms control equivalent of writing the rules and then leaving your name off the attendance sheet. Now, the International Committee of the Red Cross has been pushing for stronger restrictions. In twenty twenty-four, the ICRC issued a detailed position paper calling for a complete ban on the use of incendiary weapons in populated areas, regardless of delivery method. Their argument is essentially that the existing framework is Swiss cheese — the distinction between air-dropped and ground-launched is completely arbitrary when the effects on civilians are identical.
How's that going?
There was a meeting of CCW parties in twenty twenty-four that discussed strengthening Protocol Three, but as of mid twenty twenty-six, no new binding instrument has been adopted. The Human Rights Watch position, which they've reiterated multiple times, is that any use of white phosphorus in populated areas constitutes a violation of international humanitarian law — specifically the prohibition on indiscriminate attacks and the principle of distinction. They've documented uses in multiple conflicts.
Speaking of which — let's get to the actual documented uses. Which militaries have been caught doing this?
The list is longer than most people realize. The United States used white phosphorus extensively in Fallujah in two thousand four — that's probably the most famous case because of the documentary footage and the subsequent investigation. The US military initially denied using it as a weapon, then acknowledged using it for illumination and screening, then a documentary called "Fallujah: The Hidden Massacre" forced a wider acknowledgment. The phrase "shake and bake" entered the lexicon from that operation — that's what troops called the combination of white phosphorus and high explosives.
"Shake and bake." There's a phrase that should never have needed to exist.
Israel has used white phosphorus in multiple operations — most notably in Gaza in two thousand eight to two thousand nine, Operation Cast Lead, and again in subsequent operations. Human Rights Watch documented the use of M eight two five A one one hundred fifty-five millimeter white phosphorus shells over densely populated areas, including the UNRWA compound in Gaza City. The Israeli military initially denied it, then acknowledged it, then after international pressure announced in twenty thirteen that it would phase out the use of white phosphorus in favor of non-lethal smoke shells.
"Phase out" being the operative dodge.
It's always "phase out." It's never "we stopped yesterday." And there have been subsequent allegations in the twenty twenty-three to twenty twenty-four Gaza conflict, though the Israeli military's position is that all munitions used comply with international law. The documentation there is still being compiled by various human rights organizations.
The US, Israel — who else?
Russia has been documented using white phosphorus in multiple conflicts — in Chechnya, in Syria, and extensively in Ukraine since the twenty twenty-two full-scale invasion. There's video footage from multiple locations, including the battle for Bakhmut and the siege of Mariupol. Russian forces have used nine M twenty-two S artillery shells, which are explicitly white phosphorus munitions, and they've dropped them from drones as well.
I remember those videos surfacing. The night sky looks almost beautiful, which is the most disturbing part — these cascading white tendrils that look like fireworks, and you have to remind yourself what you're actually watching.
There's a term for that — "the aestheticization of horror." And it's a real psychological phenomenon. People see the footage and their first reaction is "that's strangely pretty," and then the cognitive shift happens and it's gut-wrenching. But to continue the list: Syria under the Assad regime used white phosphorus repeatedly during the civil war, including in Idlib province and Eastern Ghouta, often in combination with other weapons in ways that suggested deliberate use against civilian populations. Turkey has been accused of using it against Kurdish forces in northern Syria. Saudi Arabia has been documented using US-manufactured white phosphorus in Yemen.
Wait — US-manufactured?
The Saudi-led coalition used white phosphorus munitions that were manufactured and sold by the United States, which created a significant diplomatic problem because the US had restrictions on the export of incendiary weapons for use in populated areas. The State Department had to address this publicly multiple times, and the response was essentially "we're looking into it" followed by continued arms sales.
The "looking into it" to "continued sales" pipeline is the most durable infrastructure America has ever built.
It's remarkably resilient. There are also documented cases from the Nagorno-Karabakh conflict — both Armenia and Azerbaijan have accused each other of white phosphorus use, with some video evidence that independent analysts found credible. And going further back, the United Kingdom used white phosphorus extensively in both world wars, and in the Falklands conflict. The British used it in the retaking of Goose Green.
We're looking at a weapon that has been used by essentially every major military power in the modern era, and the legal framework has all the stopping power of a strongly worded email.
That's about right. And this brings us to why it's so devastating in civilian areas specifically. In open battlefield conditions, white phosphorus is horrible but its effects are somewhat contained — you're dealing with combatants, the smoke can be avoided, the burns are still catastrophic but the area of effect is limited. In a dense urban environment, everything changes.
Because the smoke doesn't just dissipate — it gets trapped.
White phosphorus smoke in a built-up area sinks into basements, into underground shelters, into the places where civilians are hiding. It's heavier than air, so it pools. And because it forms phosphoric acid on contact with moisture, you get people — children, elderly, anyone sheltering — suffering chemical burns to their eyes, their throats, their lungs, without ever being directly hit by the munition itself. This is what Human Rights Watch and the ICRC keep emphasizing: in a civilian context, the smoke is itself a weapon of indiscriminate effect.
The primary intended purpose — smoke screening — becomes the mechanism of harm.
That's the irony. The very thing the military claims as its lawful use is what makes it so indiscriminate in a city. And then there's the fire. White phosphorus ignites everything it touches. In a dense urban area with construction materials, fuel sources, gas lines — you get secondary fires that spread far beyond the initial impact zone. The phosphorus particles can be carried by wind, landing on rooftops, on clothing, on skin. The burns are thermal and chemical simultaneously, and they're extraordinarily difficult to treat. The standard first aid protocol is to submerge the affected area in water to cut off oxygen, but in a mass casualty situation in a war zone, you don't have submersion capability.
I've read that the mortality rate for white phosphorus burns is something like thirty to fifty percent even with modern medical care, and the survivors are left with horrific scarring and often lifelong respiratory damage.
That's in a well-equipped hospital. In a conflict zone with a collapsed medical system, you're looking at much higher rates. There's also a long-term environmental contamination problem. White phosphorus that doesn't ignite immediately can persist in soil and water, and when it does eventually ignite — from being disturbed, from temperature changes — it can cause injuries weeks or months after the initial attack. There are documented cases from Gaza and from Syria where children picked up what they thought were interesting rocks and suffered severe burns.
That's the legacy that doesn't make it into most coverage. The weapon keeps working long after the battle's over.
That's one of the arguments the ICRC uses for why it should be classified more restrictively — it has the same kind of post-conflict indiscriminate effect that landmines do, and we've managed to ban those.
Let's talk about the taxonomy question Daniel raised, because this is genuinely confusing and I think most people get it wrong. CBRN — chemical, biological, radiological, nuclear. Where does white phosphorus sit?
Officially, it sits outside the CBRN framework entirely. CBRN defense is about protecting against weapons that are designed to cause harm through chemical toxicity, biological pathogens, radiation, or nuclear blast. White phosphorus is none of those things by design intent. It's an incendiary. It's covered under the CCW, not the Chemical Weapons Convention. The CWC — the Chemical Weapons Convention — has a General Purpose Criterion that bans chemicals used to cause death or harm through their toxic properties, but it includes a specific exemption for "military purposes not connected with the use of chemical weapons," which covers smoke, obscurants, and incendiaries.
The CWC explicitly carves it out.
Schedule one of the CWC lists the most dangerous chemical agents — nerve agents like sarin and VX, blister agents like mustard gas. White phosphorus is not on any schedule. It's not listed at all. So from a pure legal taxonomy standpoint, a CBRN defense specialist would say white phosphorus falls under "conventional weapons with incendiary effects," not under chemical weapons.
From a medical standpoint, the injuries look chemical.
That's the tension. A physician treating white phosphorus burns is dealing with something that behaves more like a chemical burn than a thermal burn. The phosphoric acid formation, the deep tissue penetration, the reignition phenomenon — these are not typical burn patterns. The treatment protocols borrow heavily from chemical burn management. So you've got this weird situation where legally it's conventional, medically it's chemical-ish, and operationally it's used in ways that blur every line.
The "ish" is doing a lot of heavy lifting there.
That ambiguity is a feature, not a bug. It's precisely what allows militaries to use it while maintaining technical compliance with their treaty obligations. "We didn't violate the Chemical Weapons Convention because we weren't using it for its toxic properties — we were using it for smoke." The fact that the smoke is toxic is incidental, and the CWC explicitly allows incidental toxicity.
Which feels like saying "I didn't poison the water supply, I just happened to dump something poisonous into it for unrelated reasons.
That's the legal architecture we're working with. And it's not accidental. When the CWC was being negotiated in the early nineteen nineties, there was a deliberate carve-out for smoke and incendiary munitions because every major military uses them and nobody wanted to give them up. The US in particular insisted on the exemption.
If you're a CBRN defense planner, do you include white phosphorus in your threat modeling or not?
This is where it gets interesting. In practice, yes — most modern CBRN defense planning includes a category for "toxic industrial materials" and "non-traditional agents" that covers things like white phosphorus smoke, riot control agents, and various smokes and obscurants. The US military's CBRN doctrine explicitly addresses phosphorous smokes as a respiratory hazard. The M fifty gas mask — the current US standard issue — is designed to filter out phosphorous smoke particulates and the acidic byproducts. So operationally, it's treated as a CBRN threat even though legally it isn't one.
Which means the Israeli gas mask under every sink is technically relevant here, even though we're not talking about nerve agents.
The civilian masks distributed in Israel are designed for a broad spectrum of threats, including what's called "industrial chemical release" — and white phosphorus smoke in a populated area is functionally identical to a major industrial chemical release. The masks would help. Not perfectly — you'd still have skin exposure issues — but the respiratory protection is meaningful.
The taxonomy Daniel's asking about — the short answer is: white phosphorus is legally a conventional incendiary, medically a chemical-thermal hybrid, operationally treated as a CBRN-adjacent threat, and the gaps between those categories are where all the controversy lives.
That's a very clean summary. I'd add one more layer: there's a growing movement in international humanitarian law to create a new category for what some scholars call "weapons with indiscriminate area effects in populated areas" — not quite CBRN, not quite conventional, but a separate regulatory framework that would capture things like white phosphorus, thermobaric weapons, and certain cluster munitions. The Explosive Weapons in Populated Areas declaration, which was adopted in twenty twenty-two and has over eighty signatories, is a step in that direction, though it's a political declaration, not a binding treaty.
"Political declaration" being another phrase that means "we all agreed this is bad but nobody has to stop.
The gap between political declarations and binding instruments is where most of the bodies end up. But it's worth noting that even a non-binding declaration can shift norms over time. The declaration on explosive weapons in populated areas has already influenced some military operational planning. Whether it'll affect white phosphorus use specifically — the track record so far is not encouraging.
Let's pull on one thread you mentioned earlier. You said the US sold white phosphorus munitions to Saudi Arabia for use in Yemen. What's the export control situation? Is there any restriction on selling these things?
It's complicated. The US has export controls on incendiary weapons under the Arms Export Control Act, and there are policy restrictions — not statutory bans, but policy restrictions — on the transfer of incendiary weapons that are likely to be used against civilians. The problem is the "likely to be used" standard. It requires a determination that the recipient is probably going to misuse them, and that determination is made by the executive branch, which also has strategic interests in maintaining the arms relationship.
The people selling the weapons decide whether the buyer is going to misuse them.
They consistently decide "probably not," even when there's extensive documentation of misuse. After the Saudi white phosphorus use in Yemen was documented by Human Rights Watch and others, the State Department said it was "reviewing" the situation, and arms transfers continued. There was a brief pause under one administration, then a resumption under the next. The consistency across administrations of both parties suggests this isn't really a partisan issue — it's an institutional one.
The deep state's commitment to arms sales transcends partisan politics.
I wouldn't call it comforting. I'd call it a structural feature of American foreign policy. And it's not just the US — Russia exports white phosphorus munitions as well, and there's evidence of Chinese-manufactured white phosphorus appearing in various conflict zones. The supply chain for these weapons is global and largely unregulated by any binding international instrument.
Let's go back to the medical dimension for a moment, because I think it's worth understanding exactly what these injuries look like. You mentioned reignition during treatment. What's actually happening physiologically?
White phosphorus particles embed in tissue and are protected from oxygen by the body's own fluids. When a surgeon opens the wound to debride it — to remove dead tissue — the particles are exposed to air and reignite. This can happen multiple times during the same procedure, and it can happen days after the initial injury if particles haven't been fully removed. The standard treatment protocol involves continuous irrigation, keeping the wound submerged when possible, and using copper sulfate solution — which reacts with the phosphorus to form a black coating of copper phosphide that makes the particles visible and temporarily prevents reignition.
Copper sulfate — that's the stuff they use in high school chemistry to grow blue crystals.
But the use of copper sulfate is itself controversial in medical circles because it can cause copper toxicity if absorbed systemically, and it doesn't actually neutralize the phosphorus — it just makes it visible and temporarily inert. The definitive treatment is surgical removal of every single particle, which in a deep burn can mean multiple surgeries over weeks or months. And that's assuming you have access to a modern burn unit with experienced surgeons. In most conflict zones, you don't.
I'm trying to think of another weapon where the treatment itself is this nightmarish. Landmines are horrible, but once the limb is gone, the immediate threat is over. This keeps burning.
There's a reason burn surgeons who've worked in conflict zones tend to be the most vocal advocates for banning these weapons. The International Society for Burn Injuries has issued statements calling white phosphorus "uniquely cruel" among conventional weapons. And they're not a political organization — they're doctors. They're reacting to what they see on the operating table.
The "uniquely cruel" framing is striking because cruelty implies intent. But the military argument is always that the cruelty is incidental. We weren't trying to be cruel — we were trying to make smoke, and the cruelty just happened.
Which is why intent-based legal frameworks break down with weapons like this. If you judge a weapon solely by what the designer intended it to do, you can justify almost anything. What the ICRC and human rights organizations have been arguing for decades is that the effects-based standard is what should matter — not what you meant to do, but what the weapon predictably and foreseeably does when used in a given context.
A military commander dropping white phosphorus on a dense urban area can foresee exactly what's going to happen.
That's the argument. The counterargument, which you hear from military lawyers, is that foreseeability isn't the same as intent, and that international humanitarian law requires balancing military necessity against civilian harm — the proportionality test. They'd say that if the military objective is important enough, and if the commander takes feasible precautions, the incidental civilian harm may not be unlawful even if it's tragic.
Which is how you get a legal framework where burning civilians to death with phosphorus can be "proportional.
If the military objective is judged sufficiently important, yes. That's the logic of proportionality. It's not a prohibition on civilian harm — it's a prohibition on excessive civilian harm relative to the military advantage gained. And "excessive" is in the eye of the beholder.
This is the part of international law that makes me want to take a very long nap.
Yet here you are, awake and asking excellent questions.
Don't encourage me. So we've covered the documented users, the legal framework, the medical effects, the taxonomy. Is there anything on the horizon that might actually change the status quo? Any treaty negotiations, any shifts in military doctrine?
There are a few things worth watching. First, the CCW review conference is coming up — these happen every five years, and the next one is scheduled for later this year. Incendiary weapons are on the agenda, and there's a coalition of states — led by Ireland, Mexico, and a few others — pushing for an amendment to Protocol Three that would close the ground-launched loophole and strengthen the civilian protection provisions.
Ireland, interestingly enough.
Ireland has been a leader on disarmament issues for decades — they were central to the cluster munitions ban, they've been pushing on nuclear disarmament, and incendiary weapons are a priority for their diplomatic corps. But the push faces opposition from the usual suspects — the US, Russia, Israel, and a few others who argue that existing law is adequate and that the problem is compliance, not regulation.
The "laws are fine, we just need people to follow them" argument. Which is a way of saying "we don't want new laws.
It's the diplomatic equivalent of "I'm not touching you." The second thing to watch is the explosive weapons in populated areas declaration follow-up process. There's a meeting scheduled for later this year to discuss implementation, and some civil society groups are pushing to have incendiary weapons explicitly addressed in that framework. It wouldn't be binding, but it would add to the normative pressure.
Normative pressure has worked before, hasn't it? The cluster munitions ban started as a normative push and eventually became a binding treaty.
It did, but the cluster munitions ban — the Oslo Convention — also doesn't include the US, Russia, China, or Israel among its parties. So you get a treaty that binds the countries least likely to use cluster munitions and leaves out the ones most likely to. The same dynamic would probably play out with any new incendiary weapons treaty.
We're in a world where the countries that use these weapons write the rules, exempt themselves, and then argue that everything's fine because rules exist.
That's a slightly cynical but not inaccurate description of the last seventy years of arms control. The thing is, rules do matter even when they're imperfect. They shape what's considered normal. They create a basis for accountability — even if it's only political accountability, not legal. And they give human rights organizations and journalists a standard to point to when they document violations. "You violated Protocol Three" is a more powerful statement than "we think this is bad.
It's the difference between a moral claim and a legal claim.
And in the international system, legal claims carry more weight — even when enforcement is weak. So I wouldn't dismiss the normative value entirely. But I also wouldn't tell anyone to hold their breath waiting for a comprehensive ban.
Let's bring this back to the prompt's framing, because Daniel was connecting this to the gas mask conversation. There's something almost absurd about the juxtaposition — we've got these masks designed to protect against a whole spectrum of horrors, and yet one of the weapons that might actually be used in a populated area doesn't fit neatly into any of the threat categories the masks were designed for.
That's the dark comedy of civil defense planning. You prepare for the last war's threats, and the next war finds a way around your preparations. The Israeli civil defense system was built largely around the chemical weapon threat from Iraq and Syria — nerve agents, primarily. The masks were distributed, the sealed rooms were designated, the protocols were drilled. And then the threats that actually materialized were rockets, tunnel infiltrations, and in some cases, incendiary munitions that the masks help with but weren't primarily designed for.
The Maginot Line of respiratory protection.
That's painfully apt. Though I'd add that the masks do provide real protection against phosphorous smoke — it's just that they weren't optimized for it, and the public wasn't educated about that threat in the same way they were about nerve agents.
Because "nerve agent" is a clear, terrifying category. "Incendiary smoke that forms acid in your lungs" is harder to fit on a public information leaflet.
It's harder to fit in a legal category, which is where we came in. The taxonomic problem isn't just academic — it shapes what threats get prioritized, what protections get funded, and what weapons get banned.
To wrap this into something resembling an answer: white phosphorus has been documented in use by the United States, Israel, Russia, Syria, Turkey, Saudi Arabia, the United Kingdom, and others across multiple conflicts from the world wars to the present day. The primary legal instrument governing it is Protocol Three of the CCW, which bans air-dropped incendiaries in civilian areas but leaves ground-launched systems in a gray zone and exempts weapons where incendiary effects aren't the "primary purpose." The US, Israel, Russia, and China aren't parties. The CWC explicitly carves it out. Medically, it causes deep thermal-chemical burns that reignite on exposure to air, with mortality rates in the thirty to fifty percent range even with modern care. And taxonomically, it's a conventional incendiary that behaves like a chemical weapon, is treated as a CBRN-adjacent threat operationally, and occupies the gaps between legal categories that multiple militaries have been happy to exploit.
That's comprehensive. The only thing I'd add is the forward-looking piece: there's a diplomatic push to strengthen restrictions, but it faces the same structural obstacles that have blocked progress on incendiary weapons for decades. The countries that use them don't want to be restricted, and the countries that want restrictions don't use them.
Arms control in a sentence.
Now: Hilbert's daily fun fact.
Now: Hilbert's daily fun fact.
Hilbert: In nineteen oh eight, a British expedition in Somaliland nearly discovered tardigrades — those microscopic eight-legged creatures that can survive the vacuum of space and extreme radiation — when they collected moss samples from a dry riverbed. The samples were lost when a camel carrying the specimen box wandered off during a dust storm, and tardigrades would not be formally described by science for another sixty-five years.
A camel ate the first tardigrade discovery.
"Ate" is probably not accurate, but the mental image is excellent.
Thank you, Hilbert. We'll be thinking about that camel all day.
One question to leave listeners with: if the legal framework for incendiary weapons hasn't changed in decades despite consistent documentation of civilian harm, what would actually have to happen for it to change? What's the threshold?
Historically, the threshold has been either a major power deciding it wants a ban — which is how the Chemical Weapons Convention happened — or a coalition of smaller states and civil society organizations building enough normative pressure that the major powers find it politically costly to stay outside. Neither condition is currently met for white phosphorus. But these things can shift quickly when the political winds change.
This has been My Weird Prompts. Thanks to our producer, Hilbert Flumingtop, for the fact about the camel and the lost tardigrades. You can find every episode at myweirdprompts dot com. If you've got thoughts on this one, we'd love to hear them.
If you're enjoying the show, leave us a review wherever you listen — it helps other people find us. We'll be back soon.
