Trevor Ball & N.R. Jenzen-Jones
Editor’s Note: This blog post is linked to entries in the Open-source Munitions Portal (OSMP), a joint project between ARES and Airwars, available at https://osmp.ngo/.
OSMP Entry Nos. 513, 514, 548, 549, 579
The use of smoke munitions in modern conflict continues to be misunderstood by non-specialist observers. In extreme circumstances, this can lead to cases like a recent example in Ukraine, where German smoke projectiles were claimed to be chemical weapons. Smoke munitions are a standard part of the military inventory, however. Almost all modern armed forces employ smoke munitions for signalling, marking targets, and screening troop movements. In contemporary conflict zones, the most common smoke munitions are artillery gun projectiles and hand-thrown smoke grenades. Other smoke munitions, such as rockets and mortar projectiles, are less common but sometimes encountered. Whereas smoke grenades are used primarily for signalling and marking, artillery gun projectiles with a smoke payload are also regularly employed for screening purposes.
Smoke projectiles use a chemical composition—typically white phosphorus (WP) or a hexachloroethane/zinc mixture (HC)—to generate smoke for several minutes. White phosphorus is typically employed in ‘bulk’ form (in unitary projectiles) or using felt wedges soaked in WP that ignite on contact with the air (in carrier projectiles), whilst HC smoke is typically deployed in canisters ejected from carrier munitions. White phosphorus is considered the best performing composition, but is also the more hazardous due to its incendiary and toxic nature. HC, while not incendiary, is still considered toxic.
The use of WP smoke projectiles has generated controversy, sometimes as a result of observers mistaking unitary WP projectiles for those of a design much less likely to injure civilians. WP and HC smoke projectiles are also routinely misidentified; in particular, HC smoke projectiles have often been reported as WP. Reporting on the actions of the Israel Defense Forces (IDF), in particular, has often examined their use of munitions containing white phosphorus, and has been prone to confusing WP and HC types. This short article provides a comparative look at the two most common 155 mm smoke projectiles in IDF service, distinguishing them by their physical characteristics and markings, and describing their differing battlefield effects. Unitary WP projectiles are also examined herein, by way of distinguishing these in form and function from WP carrier projectiles.
The IDF employs two different models of 155 mm smoke projectile: M825-series WP rounds and the M150 HC smoke round developed and produced domestically by Elbit Systems. Both variants are based on the American M483A1 carrier projectile and have similar dimensions. Israel marks these rounds in a similar fashion, to indicate their comparable battlefield role. Both are painted with a comparable light-green base colour (sometimes called ‘blue-green’ or ‘seafoam’), and feature the same brown band on the ogive, signifying the presence of an expelling charge. Israeli M825-series projectiles have an additional maroon band marked on the ogive, above the brown band, indicating the incendiary nature of the WP-impregnated felt wedges. Israel also uses M825-series projectiles imported from the United States. These are instead marked with the U.S. colour scheme, which features the same light-green base colour with a yellow band at the ogive and red square markings to indicate an incendiary payload. The M825A1 model has an additional red band at the nose of the munition.
M825-series WP projectiles have an internal canister that carries 116 × ¾-inch (19 mm) felt wedges which are impregnated with white phosphorus (see Figure 2). This internal canister has a ‘X-rib’ in the centre, that divides the canister into four quadrants, in each of which 29 felt wedges are stacked. When the fuze functions, an expulsion charge of 51 g of M10 propellant ejects that canister out of the base of the projectile. An 0.25-inch (6.35 mm) diameter burster charge consisting of 21.2 grams of Comp A-5 located inside the expelled canister detonates after a short delay, dispersing the felt wedges. The WP wedges ignite upon contact with the air and fall to the ground burning.
By way of comparison, unitary WP projectiles contain a solid mass of WP and a central bursting charge. They are typically fitted with a point-detonating fuze, which functions upon contact with the target. The fuze detonates the central burster, rapidly dispersing the WP filler. This video shows the distinctive detonation and dispersal pattern of a conventional WP artillery projectile, in this case an American M110A1 155 mm projectile. Unitary WP may in some cases be used primarily for its incendiary effects, whereas WP carrier munitions are very rarely used in that way (ARES has recorded possible employment in this manner in Syria and Nagorno-Karabakh, but not in Gaza or Lebanon). It should also be noted that the primary purpose of M825-series WP projectiles is marking or screening. Some organisations have suggested that the use of these munitions is subject to Protocol 3 of The Convention on Certain Conventional Weapons. However, Protocol 3 clearly defines incendiary weapons as those “primarily designed to set fire to objects or to cause burn injury to persons” and explicitly exempts “Munitions which may have incidental incendiary effects, such as illuminants, tracers, smoke or signalling systems” [emphasis added].
The M150 HC projectile (see Figure 3) functions similarly to the M825-series projectiles. When the fuze functions, an expulsion charge forces the payload out of the base of the projectile. Instead of a canister containing felt wedges like the M825 series, the M150 carries 5 HC smoke canisters that are ejected and begin to burn, emitting smoke. Similar projectiles like the German DM105 or US M116 HC smoke projectiles are based on the shorter M107 155 mm projectile round, and thus only carry 4 smoke canisters.
There are several ways to determine which of these two common smoke munitions was used in a given incident. The visual signature produced upon functioning is distinctive for each of these munitions (see Figure 4). The M825 series dispenses 116 small smoke elements that tumble to the ground burning, generating the tell-tale ‘snake-like’ trails of smoke associated with the M825 series and similar munitions. By contrast, the M150 expels just 5 smoke elements, each falling to the ground burning. WP wedges will generally produce more smoke for their size, which is generally thicker and whiter in appearance (this does not take into account other materiel ignited by either type of munition).
In the case of both munitions, the projectile bodies are not destroyed after functioning—meaning they may often be found intact after impacting the ground, revealing nomenclature or other clear markings. Due to the difference in payload, especially internal construction and the number of smoke elements, the M150 and M825-series projectiles can sometimes be distinguished physically after functioning, even if no markings are visible. Pieces of the M825 internal canister, such as the x-rib or the metal casing (see Figures 5 & 6), may be found. The WP felt wedges from the M825 series may be found partially burned and can reignite when disturbed (see Figure 7). The smoke canisters from an M150 are of durable metal construction and are left intact after functioning—these, too, may be identified in the field (see Figure 8).
Technical Specifications
M825-series 155 mm artillery gun projectiles
Calibre: 155 mm
Weight: 46.53 kg
M825 length (incl. fuze): 899.16 mm
M825A1 length (incl. fuze): 886.46 mm
Smoke compound: White Phosphorus (WP)
Weight of WP mixture: 5.78 kg
Payload: 116 WP-impregnated felt wedges
M150 155 mm artillery gun projectile
Calibre: 155 mm
Smoke compound: Hexachloroethane/zinc (HC)
Weight of HC mixture: 13.5 kg
Payload: 5 HC smoke canisters
Sources
Elbit Systems. n.d. ‘Artillery Ammunition Portfolio’. <https://elbitsystems.com/media/Catalog-Artillery-Ammunition_14_Web.pdf>.
Jenzen-Jones, N.R., Patrick Senft & Yuri Lyamin. Cluster Munitions & Submunitions in Syria: A Technical Appraisal. Special Report 5. Perth: Armament Research Services (ARES). <https://armamentresearch.com/wp-content/uploads/2023/11/ARES-Special-Report-5-Cluster-Munitions-Submunitions-in-Syria.pdf>.
Khoury, Saman. 1993. M825A1 White Phosphorous Malfunction Investigation Related to the M739/M739AI Safing and Arming Module. ARDEC. <https://apps.dtic.mil/sti/tr/pdf/ADA269205.pdf>.
National Research Council. 1997–1999. Toxicity of Military Smokes and Obscurants, Vols. 1 & 2. Washington, D.C.: The National Academies Press.
Schirding, Danny. 2019. Comprehensive Advanced Artillery Solutions. Elbit Systems, Land. <https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2019/armament/Schirding.pdf>.
Shaw, Anthony P., Giancarlo Diviacchi & Ernest L. Black. 2014. Advanced Boron Carbide-Based Visual Obscurants for Military Smoke Grenades. ARDEC. <https://apps.dtic.mil/sti/tr/pdf/ADA603697.pdf>.
Triebert, Christiaan. 2017. Is the US Using White Phosphorus in Mosul? Bellingcat. https://www.bellingcat.com/news/mena/2017/03/16/is-the-us-using-white-phosphorus-in-mosul/
United States Army. 1994. Army Ammunition Data Sheets: Artillery Ammunition. TM 43-0001-28. Washington, D.C.: Department of the Army.
Header Image: “Artillery is fired by the Israeli Army into Lebanon, amid cross-border hostilities between Hezbollah and Israel, as seen from Jish, northern Israel October 2, 2024. REUTERS/Jim Urquhart” via Phil Stewart.
Remember, all arms and munitions are dangerous. Treat all firearms as if they are loaded, and all munitions as if they are live, until you have personally confirmed otherwise. If you do not have specialist knowledge, never assume that arms or munitions are safe to handle until they have been inspected by a subject matter specialist. You should not approach, handle, move, operate, or modify arms and munitions unless explicitly trained to do so. If you encounter any unexploded ordnance (UXO) or explosive remnants of war (ERW), always remember the ‘ARMS’ acronym:
AVOID the area
RECORD all relevant information
MARK the area from a safe distance to warn others
SEEK assistance from the relevant authorities