Is there a plausible military purpose for the recent use of white phosphorus in Gaza?

Question

news agencies and human rights groups have suggested Israel may have used white phosophorus in Gaza last week (the week starting Oct 8):

https://www.hrw.org/news/2023/10/12/israel-white-phosphorus-used-gaza-lebanon

https://citizenevidence.org/2023/10/13/israel-opt-identifying-the-israeli-armys-use-of-white-phosphorus-in-gaza/

https://www.cbsnews.com/news/israel-hamas-war-white-phosphorous-gaza-palestinians-amnesty-hrw-reports/

https://www.washingtonpost.com/world/2023/10/13/white-phosphorus-chemical-what-is/

https://www.france24.com/en/middle-east/20231015-ngos-accuse-israel-of-using-white-phosphorus-munitions-in-gaza-%E2%80%93-but-what-are-they

I have read it can be used as an obscurant and to mark targets. ASSUMING IT WAS USED LAST WEEK (OCT 11 AS REPORTED BY HRW), WELL IN ADVANCE OF A GROUND INVASION, are either of those or any other military use plausible here?

Answer 1

Dunno what Israel would say here precisely, but this is what the US said a while back:

The March/April 2005 issue of an official Army publication called Field Artillery Magazine reported that "White phosphorus proved to be an effective and versatile munition and a potent psychological weapon against the insurgents in trench lines and spider holes. ... We fired 'shake and bake' missions at the insurgents using W.P. [white phosphorus] to flush them out and H.E. [high explosives] to take them out".

AFAICT from the same wiki piece, Israel flatly denied using such rounds in the 2008-2009 Gaza war, despite ample visual evidence to the contrary. Actually, later it says

After the Israel Defense Forces had officially denied for months having used white phosphorus during the war, the Israeli government released a report in July 2009 that confirmed that the IDF had used white phosphorus in both exploding munitions and smoke projectiles. The report argues that the use of these munitions was limited to unpopulated areas for marking and signaling and not as an anti-personnel weapon. The Israeli government report further stated that smoke screening projectiles were the majority of the munitions containing white phosphorus employed by the IDF and that these were very effective in that role. The report states that at no time did IDF forces have the objective of inflicting any harm on the civilian population.

As for recent videos showing them being used over buildings (linked in the Q). If there's a military reason to flatten buildings, there's probably a military reasons to make their occupants not see what's coming their way, among other things. The IDF recently announced they've launched "localized" ground raids into Gaza, which may give them another plausible reason to obscure vision of building inhabitants.

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Slightly aside, there's a Protocol on Incendiary Weapons, which limits use of such weapons close to populated areas. Israel has ratified it in 1995. But it doesn't make a difference here, as Wikipedia tells us:

The protocol lists certain munition types like smoke shells which only have a secondary or additional incendiary effect; these munition types are not considered to be incendiary weapons.

The 2006 "Rules for Warefare on the Battlefield" of the IDF School of Military Law conclude that:

Phosphorus is permitted for use, as long as its use is directed against combatants and not against civilians.

(Emphasis in original.)

Answer 2

Note: I've edited all my references to "Amnesty" to "Amnesty-affiliate", but left the answer unchanged otherwise. The reason is that soon after this question was asked, one user made pretty damaging claims that the Q was promoting a hoax by someone pretending to be Amnesty, while in fact it was an official affiliate of Amnesty, though not Amnesty proper. While the original question might have been better stated, most of my answer doesn't really care all that much about the exact nature of the NGO, be it impartial or not.

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Probably not at this point, except, maybe, if they were being used as warning markers to where Israel is going to bomb (a pre-strike policy Israel uses with other types of ammo as well). I can't say if they would be safe to use in that case (doubt it).

If anything, when you try to bombard military targets embedded in civilian areas, before an actual ground assault, smoke seems like it would make it more difficult to avoid hitting civilians. IF this is indeed taking place as claimed.

However, if you take the "stacked ammo by howitzers" photos, which makes up part of Amnesty-affiliate's dossier, you have to realize a) you don't know, from the pics that they are being used now. And b) that there are perfectly valid reasons to use White Phosphorus smoke rounds once the ground assaults start (keeping in mind the risks to civilians).

Those particular shells IDed by Amnesty-affiliate - "Several of these verified photos show M825 and M825A1 artillery shells" - in the pic?

The M825/M825A1 smoke projectile is used by the artillery to produce screening smoke to obscure enemy vision or to screen maneuvering elements.

Or...

This is the American 155mm M825 and M825A1, a White-Phosphorus Smoke (WPS), base-eject, spin-stabilised, carrier projectile used to produce screening smoke to obscure enemy vision or to screen manoeuvring elements of 5-10 minutes duration.

White phosphorus rounds are a very useful way to mask attacking forces from long distance ATGM/sniper fire - both of which the IDF can expect at scale. For example, some debriefs about the Ukraine offensive start in July bemoaned the lack of smoke rounds, making long distance Russian fires more feasible.

With the caveat that they are not supposed to be used in urban areas and against civilians. There are however open fields in Gaza where they could be very useful. And also the caveat that they can probably be used very well to intentionally set buildings and people on fire.

So, no, not supportive if Israel intentionally uses WP rounds recklessly, esp. not at this time, before ground assaults. But I am also not sure Amnesty-affiliate is providing the full picture.

The legal aspects are complex:

Article 1 of Protocol III of the Convention on Certain Conventional Weapons defines an incendiary weapon as "any weapon or munition which is primarily 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". Article 2 of the same protocol prohibits the deliberate use of incendiary weapons against civilian targets (already forbidden by the Geneva Conventions), the use of air-delivered incendiary weapons against military targets in civilian areas, and the general use of other types of incendiary weapons against military targets located within "concentrations of civilians" without taking all possible means to minimise casualties.

The convention also exempts certain categories of munitions from its definition of incendiary weapons: specifically, these are munitions which "may have incidental incendiary effects, such as illuminants, tracers, smoke or signalling systems" and those "designed to combine penetration, blast or fragmentation effects with an additional incendiary effect."

The use of incendiary and other flame weapons against matériel, including enemy military personnel, is not directly forbidden by any treaty.

Gruesome as it sounds, a key metric here would be large scale occurrences of civilians killed or wounded by incendiaries. Not shown, so far, by this Amnesty-affiliate dossier.

Ultimately, this isn't really something the community here, with our imperfect access to local information and Israeli intent, is well able to give objective answers to. It could only be resolved by a formal investigation, like some of what the UN has been doing with Russia and Ukraine (for example wrt treatment of POWs).

Answer 3

Question:

Is there a plausible military purpose for the recent use of white phosphorus in Gaza?

"or any other military use plausible here?"

Short Answer:

If you give a multi-billion dollar budget to a group of very smart guys over decades, to solve an unsolvable problem like peace for Israel. They are going to redefine the problem and provide a course of action their patrons can live with.

No, no military purpose which leads to what we would recognize as victory. There is not a military solution for Israel in their troubles in Gaza. There never has been. What Israel is left with is punitive tactical actions designed to attrite their enemies and force them into a renewed truce. The use of phosphorus and other overwhelming air to ground munitions is part of the punitive.

Long Answer

Outline:

1. Background
2. Thought that went into Israeli Doctrine over the last few decades.
3. What are the tactical and strategic objectives for Israel's coming action in Gaza

Background

Beyond the phosphorus bombs, according to the IDF, it had dropped 6000 bombs on Gaza during the first 6 days of the war. Air to ground munitions which can be carried by Israel's fighters are between 500 and 2000 lbs. So that's potentially 3 million pounds of munitions Israel has dropped on one of the most densely populated areas of the world. As many as 9 thousand people per kilometer. This is most likely the beginning of an Israeli ground offensive into Gaza. Hezbollah has said a ground offensive against Hamas in Gaza would trigger their own offensive against Israel. Likewise, if the U.S. gets involved Iran has said they will be getting involved too.

Institute for the Study of War, Oct 9th 2023, IRAN UPDATE

Head of the Iranian-backed Badr Organization Hadi al Ameri threatened to attack US forces if the United States intervened in the war to support Israel.

Hezbollah and Israel are already exchanging artillery strikes in northern Israel.

Thought that went into Israeli Doctrine over the last few decades.

So why is there no military solution for Israel in Gaza? Israel occupied Gaza for 40 years after claiming it in the Six Days War in 1967. They ultimately just packed up and left Gaza in 2005, disbanding their settlements there. They did it unilaterally without any negotiations. They did it because they were constantly taking casualties and the area is so densely populated any occupying force Israel could attempt to deploy wasn't effective. If they couldn't subdue it over 40 years, they won't be able to subdue it in 2023. They don't want any part of a long-term occupation, necessary to pacify Gaza. A ground offensive when it occurs will be temporary and designed to shock, awe, and punish Hamas and ultimately Gaza. Israel has called up 300,000 IDF reserves, which gives Israel with 9 million residents an army right now about a third of the size of the U.S. with 330 million residents. That's a huge burden both logistically and economically. It's likely Israel can't keep this level of mobilization for very long. Israel will necessarily be looking to make this a short brutal affair, designed to make sure it doesn't happen again anytime soon. They can't afford to be careful or indecisive.

So why is Israel pursuing military means if there is no military solution? It's not like they haven't really thought about this. Israel has long understood there is no military path to victory leading to the pacification of Gaza. In the 1990's - 2010s the IDF operated under a complicated and ideologically dense doctrine known as Systemic Operational Design. It advised heavy dependence on the Air Force and deprioritized the infantry. Israel's "defeat" in the 2006 Winter War with Hezbollah lead to the IDF dropping this doctrine and then adopting "Plan Gideon" in 2015. Plan Gideon, changed the meaning of Decisive Victory for the IDF. It acknowledged no military victory was possible, and alternatively argued for a set of policies to manage its antagonists and prolong the peace, calling that the only victory achievable. Israel would fight Hamas every so often to keep them weak and likened that to lawn maintenance or "mowing the grass".

Plan Gideon

ADDRESSING THE NONSTATE CHALLENGE IN GAZA AND LEBANON

But Decisive Victory was meant as a major departure from past practices. The first difference is that Kochavi (Chief of General Staff of the IDF, General Aviv Kohavi, in office beginning 2019) and his staff were more publicly assertive and confident about their policy than previous commanders. The second difference is that previous documents underscored that objectives of military campaigns were to be limited. As the 2015 IDF doctrine acknowledges, these operations cannot achieve the destruction of the enemy but only the weakening of its capacities—hence the idea of a “campaign between wars” or, as colloquially described by IDF officers, operations aimed at “mowing the grass.”3 This implied abandoning the historical proclivity of the IDF for offensive doctrine

Plan Gideon, was replaced in 2020 by a plan called Decisive Victory.

What are the tactical and strategic objectives for Israel's coming action in Gaza

Eran Ortal, head of the IDF DAOW Center for Interdisciplinary Military Studies citing the Decisive Victory plan describes what an invasion of Gaza will look like and what would be Israel's objectives.

TURN ON THE LIGHT, EXTINGUISH THE FIRE: ISRAEL’S NEW WAY OF WAR

Because rocket fire on the home front has become the main threat facing Israel, the concept I describe here involves a persistent dilemma between concentrating force and diffusing it. Concentrating force is necessary for creating momentum and knocking the enemy off balance. However, a concentrated attack leaves active launch sites on the force’s flanks and does not remove the threat to the home front. Although numerous rounds of conflict have taken place in both Lebanon and the Gaza Strip, the Israeli military has thus far not launched a full-scale ground attack designed to protect the home front from rockets and missiles.

A “turn on the light and extinguish the fire” maneuver would be able to attack deep into enemy territory to conquer main nerve centers and inflict a decisive defeat, while suppressing enemy rockets and missiles launched nearby toward Israeli forces and toward the home front. The force would protect itself and the home front from missiles and rockets. It would also avoid more traditional, complex, and risky seek-and-destroy missions by striking only selected targets, thereby shortening the battle. If necessary, fire suppression assets could also be deployed outside the main force’s path of advance, supported by dedicated assault and security forces.