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Smoke screen

A smokescreen is a mass of dense smoke deployed to conceal military units, areas, or activities from enemy observation by reducing visibility through the scattering or absorption of light. In a figurative sense, it denotes any tactic, statement, or device designed to obscure, confuse, or mislead others, often to divert attention from a true intention or fact.^[1] Smoke screens have been employed in warfare since at least the American Civil War in 1862, when black smoke was used in naval operations to hinder enemy sighting.^[2] The United States Army began systematic experimentation with smoke and obscurants during World War I, expanding their use extensively in World War II for both ground and naval applications, including large-scale screens to protect cities from aerial bombing.^[3] British forces, for instance, deployed massive smoke operations in 1940–1941 to shield industrial centers from German air raids.^[4] In military doctrine, smokescreens primarily function through four roles: screening to hide friendly movements in one's own territory or between forces; obscuring to degrade enemy vision of targets; deceiving to mislead about operational intentions; and signaling or identifying positions for friendly units.^[5] They are produced via chemical munitions such as grenades, artillery shells, mortar rounds, or vehicle-mounted generators that release aerosols like hexachloroethane or red phosphorus, creating persistent clouds tailored to environmental conditions.^[5] Offensively, smokescreens conceal advancing infantry, tanks, or aircraft; mask breaches in obstacles; and support amphibious landings by screening beachheads from defenders.^[5] Defensively, they blind observation posts, isolate enemy advances for counterattacks, and impair guided weapons like anti-tank missiles by limiting laser or infrared targeting.^[5] Operations range from hasty, short-duration screens at the battalion level to deliberate, large-area deployments coordinated at brigade or higher echelons.^[5] Contemporary developments emphasize multispectral obscuration, with U.S. Army initiatives in 2025 focusing on smoke obscurant munitions (SOM) that not only block visible light but also disrupt infrared, radar, and other sensors through advanced chemical formulations, enhancing protection against modern precision-guided threats.^[6]

Principles of Operation

Visual Obscuration Mechanisms

Smoke screens achieve visual obscuration primarily through the dispersion of aerosol particles that interact with visible light via scattering and absorption, reducing the transmission of light from target areas to observers. These particles, typically in the size range of 0.7 to 50 µm, form a cloud that blocks line-of-sight by attenuating incoming and reflected light, thereby concealing movements or positions. The effectiveness depends on achieving a high particle concentration to ensure sufficient optical density across the desired coverage area.^[7] The dominant mechanism for light interaction in such clouds is Mie scattering, which occurs when aerosol particles have diameters comparable to the wavelength of visible light (approximately 0.4–0.7 µm). Mie theory describes how these particles scatter light asymmetrically, with forward scattering predominating, leading to a diffuse haze that significantly reduces visibility. For optimal obscuration in the visible spectrum, particle sizes around 0.3–1 µm maximize the extinction efficiency, as smaller particles undergo Rayleigh scattering (ineffective for broadband visible blocking) and larger ones settle more quickly. The mass extinction coefficient, which quantifies this attenuation per unit mass of aerosol, is derived from Mie calculations and varies with particle size distribution and refractive index.^[8]^[9] Particle density and dispersion are critical for maintaining obscuration over time and space. High initial density, modeled as a Gaussian concentration profile C(r) = \frac{Q_i}{(2\pi)^{3/2} \sigma_x \sigma_y \sigma_z} \exp\left(-\frac{1}{2} \left[ \frac{(x-x_i)^2}{\sigma_x^2} + \frac{(y-y_i)^2}{\sigma_y^2} + \frac{(z-z_i)^2}{\sigma_z^2} \right]\right), ensures rapid buildup of optical depth, where Q_i is the source strength and \sigma terms represent dispersion scales. Dispersion widens the cloud, but excessive spreading dilutes density and shortens effective duration, typically limiting coverage to minutes without resupply.^[9] The degree of obscuration is quantified by optical depth \tau, defined by the Beer-Lambert law as \tau = -\ln(I / I_0), where I is the transmitted light intensity and I_0 is the initial intensity. This \tau = \int \alpha C(r) \, dr, with \alpha as the mass extinction coefficient and C(r) as local concentration, must exceed 3–4 for near-total visible blockage over typical path lengths. Environmental factors like wind accelerate dispersion by advecting the cloud centroid at speeds up to several m/s, potentially halving duration in moderate breezes, while high humidity promotes particle growth through coagulation or hygroscopic effects, altering size distribution and reducing scattering efficiency by up to 20–30%. These mechanisms can be extended briefly to multispectral screening by adjusting particle properties for broader wavelength coverage.^[10]^[9]

Multispectral Screening

Multispectral screening extends the foundational principles of visual obscuration to broader electromagnetic spectra, enabling smoke screens to counter advanced sensors beyond human sight.^[11] Infrared obscuration relies on aerosol particles that either absorb or reflect thermal radiation, attenuating signals in the infrared spectrum (0.7–14 μm) where thermal imaging devices operate. Absorptive particles, such as those derived from red phosphorus or metal-organic frameworks, convert incident infrared energy into heat, reducing transmittance through blackbody emission matching the target's thermal signature. Reflective mechanisms involve dielectric or metallic particles that scatter infrared wavelengths via Mie scattering, particularly effective for longer wavelengths in the mid- and long-wave infrared bands used by common thermal imagers. These processes achieve extinction coefficients that can reduce visibility to under 10% within seconds of deployment, depending on particle size distribution optimized for the target spectrum.^[12]^[13]^[14]^[9] Development of multispectral smokes has focused on formulations that simultaneously obscure visible light (0.4–0.7 μm), near-infrared for laser designators (around 1.06 μm), and thermal infrared for imaging sensors, addressing the limitations of traditional hexachloroethane-based smokes that primarily target visible wavelengths. Early efforts in the 1990s explored carbon-based aerosols for broadband attenuation, but modern compositions incorporate advanced nanomaterials, such as electrospun conductive nanofibers, to enhance performance across ultraviolet, visible, and infrared regions. These advances counter thermal imaging by disrupting heat contrast and jamming laser designators through spectral absorption at operational wavelengths, as demonstrated in U.S. Army trials with vehicle-mounted systems. In contrast to the narrower visible range, the extended infrared spectrum requires particles tuned to larger sizes (1–10 μm) for efficient interaction with longer wavelengths, ensuring comprehensive sensor denial. As of 2025, ongoing research includes ultra-thin fibers for microwave obscuration and perovskite materials for multi-wavelength effects.^[15]^[14]^[13]^[16]^[17] Specific adaptations include coded visibility smokes, which provide directional transparency to allow friendly forces visibility while blocking adversaries, as pursued in U.S. military research. The Defense Advanced Research Projects Agency's Coded Visibility program, initiated in July 2022, develops tunable aerosols using polarized or patterned particles that exploit differences in observer equipment or position, enabling one-way infrared transmittance in the 0.78–14 μm range. This approach builds on patent-protected methods for asymmetric obscuration, where smoke appears opaque from one direction due to angular scattering but permeable from another, enhancing tactical advantages without compromising allied sensors. Such innovations prioritize safety and controllability, avoiding hazardous materials like white phosphorus.^[18]^[19]^[20]

Historical Development

Early and Pre-20th Century Uses

The use of smoke for military concealment has ancient origins, with the first documented instance circa 2000 BC in the wars of ancient India, where incendiary devices and toxic fumes were used to create obscuring smoke during battles. Similar techniques appeared in other ancient conflicts, where natural fires or burning vegetation served to obscure troop movements, though these methods were often opportunistic rather than systematically planned.^[21] In medieval warfare, smoke generation became a more deliberate tactic among nomadic forces. During the Mongol invasion of Europe in 1241, at the Battle of Legnica, Mongol commanders exploited smoke—likely produced by burning reeds or dry grass—to confuse Polish and allied knights, separating their cavalry from infantry and enabling flanking maneuvers that led to a decisive victory.^[22] Such applications typically involved simple pyrotechnics like straw, wet hay, or other flammable organic materials set ablaze to create dense clouds, allowing raiders or armies to advance or retreat under cover. However, these primitive methods had significant limitations: smoke dispersal was heavily dependent on wind direction and speed, often rendering screens unpredictable and short-lived, while the labor-intensive preparation restricted their scale and reliability in prolonged engagements.^[21] By the 19th century, smoke screens saw application in more structured conflicts, exemplified during the American Civil War. In 1863, Confederate General Robert E. Lee employed combustion of coal and oil to generate obscuring smoke, aiding the concealment of troop withdrawals and supply movements amid Union pursuit.^[23] This marked an evolution from purely natural fires, incorporating readily available industrial byproducts for denser, more persistent cover. Toward the late 19th century, military thinkers began exploring chemical enhancements, with proposals for reactive mixtures that could produce controlled smoke without open flames, setting the stage for industrialized applications.^[24]

20th Century Conflicts

The introduction of smoke screens in World War I represented a pivotal shift in tactical obscuration, evolving from ad-hoc methods to systematic deployment for concealing infantry and naval advances. The British pioneered the first notable use during the Dardanelles campaign in 1915, where naval forces employed smoke lighters towed by trawlers to generate protective screens during the Gallipoli landings on April 25, concealing troop movements from Ottoman artillery and machine guns along the beaches.^[25] This innovation, though hampered by variable winds and limited chemical formulations like oil-based emissions, allowed initial waves of Allied troops to establish beachheads despite heavy resistance, demonstrating smoke's potential to disrupt enemy observation without lethal effects. Concurrently, the Germans introduced smoke grenades around 1916, using chlorosulfonic acid in devices like the Nebelbombe to produce dense white clouds for masking trench raids and counter-battery fire, enhancing close-quarters assaults throughout the war.^[26] By 1917, smoke screens had become integral to major offensives, particularly in the Third Battle of Ypres (Passchendaele), where British forces integrated them into creeping barrages to shield infantry advances across mud-choked terrain. During operations like the Action of 22 August 1917 near Langemarck, troops carried smoke candles—portable pots emitting chemical vapors—to create localized screens up to 100 meters wide, protecting assaults on German positions from enfilading fire and allowing advances of several hundred yards in sectors where visibility was otherwise nil due to rain and fog.^[27] This tactical employment reduced casualties by obscuring machine-gun nests and wire entanglements, though effectiveness varied with wind direction, contributing to mixed results in the broader offensive that claimed over 500,000 casualties on both sides.^[28] World War II saw expanded integration of smoke into combined-arms tactics, with Allied forces refining creeping barrages to include 10-20% smoke shells for enhanced concealment during amphibious and inland assaults. In operations like the Battle of the Reichswald in February 1945, British and Canadian artillery laid yellow smoke markers ahead of high-explosive lifts, enabling infantry to advance 1-2 kilometers under cover against fortified German lines, minimizing exposure to 88mm guns and snipers in the Siegfried Line.^[29] Naval applications proliferated in the Pacific theater, where U.S. Navy destroyers routinely deployed smokescreens using fumigators and pyrotechnic pots to shield carrier task forces; a prime example occurred during the Battle off Samar on October 25, 1944, when USS Heermann and accompanying escorts generated a 5-mile-wide screen of hexachloroethane-based smoke, frustrating Japanese battleship Yamato's gunnery and allowing Taffy 3's jeep carriers to evade destruction despite overwhelming odds.^[30] In the 1991 Persian Gulf War, coalition forces extensively used smoke screens, including vehicle-mounted generators producing fog oil plumes, to conceal advances and degrade Iraqi targeting during operations like the ground campaign to liberate Kuwait. This employment highlighted the integration of smoke with modern sensors, though limited by desert winds.^[31] During the Cold War era, smoke screen usage remained constrained by international treaties like the 1925 Geneva Protocol, which blurred distinctions between non-lethal obscurants and prohibited chemical agents, leading to cautious employment in Korea and Vietnam to avoid escalation accusations. In the Korean War, U.S. Army chemical units, such as the 71st Smoke Generator Company, deployed jeep-mounted M1 generators producing fog oil plumes to screen key ports like Inchon and Pusan from North Korean air reconnaissance, operating intermittently from 1950-1953 to cover evacuations and supply lines without broader offensive integration due to fears of reprisal under chemical warfare bans.^[32] Similarly, in Vietnam, restrictions limited widespread tactical smoke amid scrutiny over herbicides like Agent Orange, though specialized "smoke ships"—helicopters modified with exhaust oil injectors—provided localized aerial screens for troop insertions, as seen in Air Mobile operations from 1965 onward, prioritizing defensive concealment over aggressive maneuvers.^[4]

Technologies and Delivery Methods

Portable and Ground Devices

Smoke grenades serve as primary handheld devices for infantry to deploy smoke screens rapidly in mobile or close-quarters operations, enabling concealment during advances or retreats. These pyrotechnic munitions, such as the U.S. Army's AN/M8 white smoke grenade and M18 colored smoke grenade, feature a cylindrical sheet metal body approximately 2.5 inches in diameter and 5.5 inches long, filled with a smoke-producing composition like hexachloroethane (HC) for white smoke or dye-infused mixtures for colored variants. Ignition occurs via a standard M204A1 or M201A1 fuze with a 1.2- to 2-second delay after the safety pin is pulled and lever released, allowing safe throwing without premature activation.^[33] Soldiers can typically throw these grenades up to 30-40 meters, depending on physical conditioning and terrain, providing immediate visual obscuration over an area of about 20-30 meters in diameter.^[34] Burn times range from 50 to 90 seconds, during which they emit dense smoke at rates sufficient to screen small teams from direct observation, though effectiveness diminishes in windy conditions.^[35] For ground-based artillery support in portable scenarios, smoke shells like the M375 105mm howitzer cartridge employ HC mixtures to generate broader screens from man-portable or towed artillery positions. These shells consist of a bursting charge that disperses the HC composition—typically 45-50% hexachloroethane, 28-30% zinc oxide, 15-20% aluminum, and 5-10% ammonium perchlorate—upon impact or airburst, creating a smoke cloud lasting 2-5 minutes over 200-400 meters.^[36] The HC formulation produces zinc chloride particulates that effectively obscure visible and near-infrared spectra, with emission rates around 10-15 m³/s in calm winds, allowing infantry units to request fire support for tactical masking without dedicated vehicle systems.^[37] Portable smoke pots and backpack generators provide sustained ground cover for defensive positions or ambushes, deployable by individual soldiers or small units. The M8 screening smoke pot, a steel canister weighing about 25 pounds when filled, ignites via a pull-wire fuze to burn for 3-5 minutes, producing approximately 100,000-150,000 cubic feet (2,800-4,200 m³) of smoke at rates of 10-20 m³/s, suitable for obscuring a 50-100 meter front.^[38] Larger variants like the M1 land smoke pot extend this to 10-15 minutes of emission, using similar HC fillers in a 15-20 pound pot that can be hand-carried and placed for static screening.^[39] These devices prioritize ease of transport, with pots requiring no external power. Safety protocols for troops emphasize minimizing exposure to toxic byproducts like hydrochloric acid from HC smokes, mandating that personnel remain upwind during deployment and ignition to avoid respiratory irritation. Gloves must be worn when handling or throwing grenades and pots to prevent chemical burns from hot casings reaching 200-300°C, and entry into smoke plumes requires full protective masks, long-sleeved uniforms, and head coverings.^[40] Training doctrines prohibit use in enclosed spaces without ventilation and limit exposure durations to under 15 minutes without gear, with post-use decontamination using water to neutralize residues.^[41] Such measures ensure operational effectiveness while mitigating health risks in field conditions. For larger-scale applications, these portable systems can integrate with vehicle-mounted generators to extend coverage across broader fronts.

Vehicle-Mounted and Large-Scale Systems

Vehicle-mounted smoke systems on tanks and armored personnel carriers (APCs) enable rapid deployment of obscurants for self-protection and maneuver concealment. These typically consist of multi-tube grenade launchers that fire pyrotechnic smoke grenades to create instantaneous screens. For instance, the Russian T-72 main battle tank features eight 81-mm smoke grenade launchers mounted on the left side of the turret, capable of launching up to 32 grenades to produce a protective smoke veil around the vehicle.^[42] Complementing this, the T-72's exhaust smoke system injects fuel into the engine exhaust to generate a trailing smoke cloud while the vehicle moves at speeds up to 25 km/h, enhancing mobility under cover.^[42] Similarly, U.S. APCs like the M113 employ the M239 smoke grenade launcher system, with one four-tube cluster on each side of the hull that simultaneously fires eight 66-mm smoke grenades total for immediate visual obscuration during tactical repositioning.^[43]^[44] In naval applications, shipboard smoke generators provide fleet-level protection by deploying dense aerosol clouds to mask vessel formations from visual and infrared detection. Modern systems often use portable pots or line-charge dispensers that release chemical aerosols, such as those tested for countering anti-ship missiles and satellite surveillance.^[45] These setups, evolved from historical designs like the U.S. Navy's Mark 1 Mod 1 generator with four tanks producing continuous smoke via vaporized fuel oil, now emphasize rapid activation for defensive screens during high-threat scenarios.^[46] Aerial dispensers on aircraft carriers or support ships can further extend coverage, laying linear smoke trails to obscure entire task forces.^[47] Large-scale ground systems, such as the U.S. Army's M56 Coyote, deliver sustained battlefield obscuration from vehicle platforms to deny enemy observation over wide areas. Mounted on a High Mobility Multipurpose Wheeled Vehicle (HMMWV), the M56 integrates a smoke generating unit with a 120-gallon fuel tank and power unit, producing 90 minutes of visual/near-infrared smoke or 30 minutes of mid-infrared obscuration without resupply by atomizing fog oil through a turbine.^[48] This system supports division-level operations by creating dynamic screens up to several kilometers in extent, protecting maneuvering forces from reconnaissance.^[49] Its successor, the M75 Screening Obscuration Module (SOM), offers a lighter, 60-pound vehicle-mountable alternative using kerosene or diesel to generate targeted smoke clouds for breaching and concealment.^[50] Post-2010 developments have integrated smoke delivery with unmanned systems for enhanced precision and reduced risk. The U.S. M75 SOM, for example, can be transported by the TRV-150 tactical resupply drone, allowing remote deployment of obscurants in contested zones.^[50] In the Ukraine conflict, Russian forces have employed first-person-view (FPV) drones to lay smoke screens by maneuvering the aircraft to disperse payloads, creating temporary covers that obscure infantry assaults from direct fire and drone spotters while compensating for wind drift.^[51] These adaptations extend vehicle-mounted capabilities to aerial platforms, enabling layered, on-demand area denial.

Chemical Agents

Traditional Smoke-Producing Chemicals

Traditional smoke-producing chemicals, employed primarily in military applications from the early to mid-20th century, relied on hydrolysis or combustion reactions to generate dense aerosols for visual obscuration. These agents, such as zinc chloride-based formulations, chlorosulfuric acid mixtures, titanium tetrachloride, white phosphorus, and red phosphorus compositions, produced smoke through interactions with atmospheric moisture or ignition, often resulting in hazardous byproducts. Their effectiveness stemmed from the formation of fine particles that scattered light effectively, though many posed significant health risks due to corrosiveness and toxicity.^[52] Zinc chloride (HC) smoke was generated by combusting a pyrotechnic mixture of hexachloroethane (C₂Cl₆), zinc oxide (ZnO), and aluminum, yielding approximately 62.5% zinc chloride (ZnCl₂) by mass in the resulting smoke. The reaction proceeds exothermically as C₂Cl₆ + ZnO → ZnCl₂ + carbon products, with the ZnCl₂ vapor cooling and nucleating into submicron aerosols that enhance obscuration upon reacting with water to form hygroscopic particles. This process created dense, persistent white smoke suitable for ground-based munitions like grenades and artillery shells. However, ZnCl₂'s corrosiveness led to severe toxicity concerns, including pulmonary edema and respiratory distress at concentrations above 1,700–2,000 mg·min/m³, with lethal exposures reaching 50,000 mg·min/m³ in enclosed spaces during military training.^[52]^[53]^[52] Chlorosulfuric acid (FS) smoke involved a mixture of 45% chlorosulfonic acid (HSO₃Cl) and 55% sulfur trioxide (SO₃), dispersed via vaporization or atomization in smoke generators. Upon release, SO₃ hydrolyzed with atmospheric moisture according to SO₃ + H₂O → H₂SO₄, forming a stable sulfuric acid mist that condensed into fine droplets for rapid screening, achieving obscuration within 1–3 seconds and persisting for 10–15 minutes in naval operations. This agent saw extensive use in World War II naval tactics, where it was sprayed from ships or aircraft to conceal fleets and maneuvers over areas up to 300 meters long. The resulting hydrochloric and sulfuric acids made FS highly corrosive and irritating to personnel and equipment.^[2]^[54]^[2] Titanium tetrachloride (FM) smoke was produced by hydrolyzing the liquid TiCl₄ upon dispersal into humid air, following the reaction TiCl₄ + 2H₂O → TiO₂ + 4HCl, which generated fine titanium dioxide (TiO₂) particles and hydrochloric acid vapor. The particle size, typically ranging from 0.1 to 1 µm depending on hydrolysis conditions like temperature and humidity, was critical for smoke density, as smaller particles improved light scattering and obscuration efficiency without rapid settling. This non-combustive method allowed for quick deployment from portable or vehicle-mounted devices, creating thick white clouds effective for short-range screening. The byproduct HCl contributed to the agent's irritancy, though less persistently toxic than ZnCl₂.^[55]^[56] White phosphorus (WP) smoke was generated by the ignition of white phosphorus (P₄), a waxy, pyrophoric solid that spontaneously ignites in air at around 30°C, burning to produce phosphorus pentoxide (P₄O₁₀) which rapidly hydrolyzes with atmospheric moisture: P₄O₁₀ + 6H₂O → 4H₃PO₄, forming dense phosphoric acid aerosols for visual obscuration. Used in artillery shells, grenades, and mortar rounds since World War I, WP provided immediate, persistent white smoke for screening and signaling, often combined with a bursting charge for dispersal. However, its high reactivity posed severe risks, including deep burns, toxicity from phosphorus vapors causing respiratory failure and organ damage, and environmental concerns leading to restrictions under international law as an incendiary weapon when used against personnel.^[57] Red phosphorus (RP) smoke relied on the ignition of polymeric red phosphorus ((P₄)ₙ) mixed with oxidizers like sodium nitrate and binders, igniting at approximately 280°C to produce phosphorus pentoxide (P₄O₁₀) that hydrolyzed with moisture into phosphoric acid aerosols for obscuration. This combustion-based approach, used in mortar rounds and grenades, generated persistent smoke clouds suitable for area denial, with the red phosphorus form being less spontaneously reactive than white phosphorus. Military compositions often included 80–95% red phosphorus to balance ignition reliability and smoke yield. Additives such as dyes could be incorporated to produce colored variants for signaling purposes.^[58]^[59]^[58]

Advanced and Specialized Formulations

Advanced smoke screen formulations have evolved from traditional chemical bases to incorporate modern priorities such as reduced toxicity, multispectral obscuration capabilities, and adherence to international environmental standards. These developments address the limitations of earlier agents by emphasizing safer pyrotechnic mixes that minimize health risks to personnel while maintaining effective screening in visual, infrared, and radar spectra. Research by the U.S. Army has focused on iterative improvements to legacy compositions, replacing hazardous components with less reactive alternatives to lower overall exposure hazards.^[40] Hexachloroethane (HC)-based mixtures have been reformulated to reduce toxicity, often substituting zinc oxide or chloride with compounds like stannous oxide and aluminum to produce white smoke comparable to older zinc-based versions but with lower environmental and health impacts. These updated HC compositions, developed by the U.S. Army's DEVCOM Chemical Biological Center, avoid the severe pulmonary injuries associated with zinc chloride aerosols while providing similar obscuration duration and density for grenades such as the M18. The goal is to achieve lethal concentration 50 (LC50) values indicative of minimal acute inhalation risk, aligning with safety thresholds that prevent fatalities from short-term exposures during training or operations.^[60]^[52] For multispectral applications, graphite and metal flake composites serve as radar-attenuating additives in smoke clouds, enhancing electromagnetic obscuration beyond visible light blocking. Graphite flakes, dispersed in pyrotechnic mixes, effectively scatter millimeter-wave and infrared signals, providing broadband protection against detection systems; when combined with metal flakes such as copper or aluminum, these composites extend attenuation into radar frequencies, floating longer than heavier metal chaff alone to maintain persistent screens. U.S. military research highlights their use in field-deployable obscurants to counter advanced sensors, with formulations tuned for particle size to optimize suspension time and signal jamming efficiency.^[61]^[62]^[63] Non-pyrophoric alternatives to white phosphorus, such as boron carbide-based compounds, represent a key advancement in safe, incendiary-free smoke production. U.S. Army investigations, including work by RDECOM-ARDEC and ECBC, have developed B4C/KNO3 mixtures with potassium chloride diluents and burn-rate modifiers like calcium stearate, yielding smoke grenades that outperform standard M83 TA phosphorus rounds in obscuration mass and duration without ignition risks or toxic byproducts. These boron formulations, tested in smoke chambers and field trials, support compliance with restrictions on pyrophoric materials by using benign oxidizers and fuels, with ongoing assessments confirming low inhalation toxicity profiles. Although initial prototypes date to 2014, subsequent refinements continue to refine particle granulation for dust reduction and performance tuning.^[64] Specialized additives like dyes and sulfonic acids enable persistent or colored smokes for signaling and extended screening. Anthraquinone derivatives, such as 1-N-methylaminoanthraquinone, produce vivid red smoke when vaporized in pyrotechnic reactions, offering high-purity coloration for identification markers with molecular weights optimized for aerosol stability. Sulfonic acids, including chlorosulfonic acid in liquid-dispersed formulations, generate dense, long-lasting white fogs by reacting with atmospheric moisture, historically used in military sprays for rapid area denial but now integrated into safer mixes to enhance persistence without excessive acidity. These elements are selected to meet formulation goals of environmental compliance, including lower LC50 thresholds to avoid classification as toxic chemicals under the 1993 Chemical Weapons Convention, which prohibits agents with significant incapacitating effects while permitting non-lethal obscurants.^[65]^[2]^[66]

Tactical Employment

Land-Based Tactics

In land-based tactics, smoke screens have been employed offensively to facilitate infantry advances by concealing movements from enemy observation and providing cover during assaults. A prominent example is the creeping barrage during World War I, where artillery fire, often incorporating smoke shells, advanced incrementally ahead of infantry to suppress defenders and obscure the attackers' positions, as seen in British operations from 1917 onward that integrated smoke with shrapnel for enhanced concealment.^[67] This tactic evolved into combined smoke and explosive barrages that allowed troops to cross open terrain with reduced exposure to machine-gun fire. In the Vietnam War, U.S. forces utilized smoke grenades and generator units to screen airmobile infantry insertions and ground advances through dense jungle, masking troop concentrations from enemy spotters and enabling surprise maneuvers despite limited large-scale obscuration compared to earlier conflicts.^[32] Defensively, smoke screens serve to obscure retreats and fortifications, denying visual targeting to enemy artillery and observers. During the Korean War, the U.S. 338th Smoke Generator Company maintained a continuous smoke screen over four months near Pork Chop Hill from November 1952 to February 1953, significantly reducing the effectiveness of North Korean artillery fire on entrenched positions and allowing defenders to reposition without detection.^[32] Similarly, in World War II's Battle of Metz, American engineers and infantry used smoke pots to veil bridgeheads across the Moselle River, protecting fortifications and withdrawal movements from German counter-battery fire.^[68] These applications highlight smoke's role in channeling enemy advances into kill zones or buying time for defensive consolidations by disrupting line-of-sight targeting. Smoke integrates seamlessly with combined arms operations to deny artillery spotting and support tank assaults, enhancing overall maneuverability. By obscuring forward observers and enemy target acquisition systems, smoke isolates opposing forces and protects advancing armor; for instance, in the 1973 Yom Kippur War, Egyptian smoke operations across the Suez Canal concealed tank crossings and reduced Israeli aerial spotting, enabling five divisions to advance 100,000 personnel in 24 hours.^[69] In tank assaults, smoke generators and munitions provide immediate cover for breaching obstacles, as demonstrated in Soviet tactics during World War II where tank battalions advanced through smoke corridors created by mortar-delivered chemicals to shield against anti-tank guns.^[70] This synchronization with artillery, mortars, and infantry multiplies combat power while minimizing friendly losses from visual-based threats. U.S. Army doctrine, as outlined in FM 3-50 Smoke Operations, emphasizes employment thresholds based on METT-TC factors—mission, enemy, terrain and weather, troops and support available, time, and civil considerations—to ensure smoke enhances rather than hinders operations. Planning must account for unit proficiency in low-visibility conditions, with smoke timed to key decision points to avoid interfering with friendly target acquisition or movement; for example, "base the planning factor on METT-T and the proficiency of your unit to operate under smoke as shown in previous combat (or training) operations."^[69] Adaptations from naval tactics have influenced amphibious land operations, such as smoke veils at Anzio in 1944 to screen beachhead defenses.^[32]

Naval and Aerial Tactics

In naval warfare, smoke screens have been employed to obscure fleet movements and evade enemy gunfire, particularly during World War II. During the pursuit of the German battleship Bismarck in May 1941, British forces, including HMS Prince of Wales, deployed smoke to cover their withdrawal after sustaining damage in the Battle of the Denmark Strait.^[71]^[72] These tactics relied on destroyer-launched smoke to create dense curtains that reduced visibility for optical gunnery, allowing damaged vessels to disengage without immediate pursuit.^[73] In amphibious operations, smoke corridors were critical for establishing safe paths from ships to shore, shielding landing craft from coastal defenses. During World War II rehearsals and assaults, such as those in the Pacific theater, naval forces laid ship-to-shore smoke screens using generators and artillery to mask the approach of assault waves, preventing enemy observation and fire on vulnerable boats.^[30] For instance, in operations like the Marianas campaign, integrated smoke tactics concealed fleet positions and created protective lanes, enabling troops to reach beaches under reduced enemy interdiction.^[74] This combined naval-air effort often involved aircraft dropping smoke pots to extend corridors inland, minimizing casualties during the critical landing phase. Aerial tactics incorporating smoke screens focused on evasion and support roles, with aircraft deploying them to protect formations or enhance ground operations. In World War II, U.S. Army Air Forces used M10 smoke tanks on fighters and light bombers to lay aerial screens, concealing troop movements or disrupting anti-aircraft fire during close air support missions.^[75] In the Pacific theater, smoke from M10 tanks aided in masking carrier-based strikes. In close air support, smoke not only marked targets for precision strikes but also screened attacking aircraft from ground fire, allowing low-level passes with reduced exposure. Modern naval tactics have revived interest in smoke screens for defense against advanced threats, including missiles. A 2022 analysis by the U.S. Naval Institute proposed reintegrating smokescreens into fleet operations, arguing that despite radar's dominance, they could counter loitering munitions, drones, and anti-ship missiles by obscuring visual and infrared signatures in contested environments.^[47] This evolving role emphasizes rapid-deployment systems, such as infrared-obscuring aerosols, to create temporary "fog of war" against hypersonic and autonomous threats, potentially complementing electronic countermeasures in high-speed engagements.^[16]

Modern Developments and Limitations

Contemporary Military Applications

In post-2000 conflicts, particularly in Iraq and Afghanistan, U.S. military forces utilized smoke screens extensively for convoy protection and urban operations to obscure movements and deny enemy observation. For instance, during urban engagements in Buhriz, Iraq, in 2007, soldiers from the 1st Stryker Brigade Combat Team deployed smoke grenades to provide immediate concealment while engaging insurgent forces.^[76] These applications drew on foundational doctrines from earlier wars but adapted to asymmetric threats, where smoke helped mitigate improvised explosive devices and sniper fire during patrols and logistics movements.^[77] The U.S. Army announced advancements in its next-generation smokescreen program in 2025, focusing on concealment in drone-dominated environments. The M75 Screening Obscuration Module (SOM), first employed operationally that year, replaces the legacy M56 Coyote system and offers lighter weight, faster deployment, and enhanced multispectral obscuration to counter unmanned aerial surveillance and targeting.^[6] This development addresses the proliferation of low-cost drones observed in recent conflicts, enabling forces to mask maneuvers against advanced reconnaissance.^[78] NATO has pursued standardization of multispectral smoke munitions through collaborative studies and agreements to ensure interoperability among member states. A key 1980s report by Sub-Panel VI detailed requirements for multi-spectral screening smokes, influencing subsequent munitions development for visual, infrared, and radar obscuration in joint operations.^[79] These efforts support unified deployment in multinational scenarios, with compatible systems meeting NATO STANAG criteria. Contemporary training emphasizes smoke integration in simulations against peer adversaries like China and Russia, preparing forces for large-scale combat operations (LSCO). Virtual and live-fire exercises, such as those outlined in U.S. Army doctrine, incorporate smoke screens for close fire support and obscuration during contested maneuvers, simulating high-intensity environments with electronic warfare and precision strikes. Multinational events like Combined Resolve further test these tactics, using smoke to replicate battlefield denial against near-peer threats in urban and open terrain.

Countermeasures and Environmental Considerations

Countermeasures to smoke screens primarily rely on advanced sensor technologies and tactical adjustments that exploit the limitations of obscurants. Thermal imaging systems can often bypass traditional smoke by detecting heat signatures that particles do not fully obscure, though specialized multispectral imaging in the short-wave infrared (SWIR) range has proven particularly effective in penetrating military-grade screening smoke, revealing movement and details invisible in the visible spectrum.^[80] Wind dispersion tactics further undermine smoke effectiveness, as varying wind speeds and directions can rapidly dilute or shift screens, requiring operators to account for meteorological conditions to maintain coverage, with low winds allowing longer persistence while stronger gusts necessitate increased munition expenditures.^[5] Radar systems penetrate smoke screens with minimal interference, as the wavelength of radar waves exceeds the size of smoke particles, enabling detection of targets regardless of visual or infrared obscuration.^[81] Environmental effects of smoke agents pose significant risks to ecosystems, particularly from formulations like hexachloroethane (HC) smoke, which produces zinc chloride as a byproduct. Zinc chloride exhibits toxicity in soil and water, where it contributes to chloride accumulation and forms less mobile zinc species that can alter pH levels and bioaccumulate, potentially harming aquatic life and vegetation in contaminated areas.^[82] White phosphorus (WP), historically used in smoke munitions for its obscuring properties, faces restrictions under Protocol III of the 1980 Convention on Certain Conventional Weapons (CCW), which prohibits or limits incendiary weapons—including WP when employed to cause burns—against civilian concentrations or in ways that endanger non-combatants, due to its persistent burning and toxic residues.^[83] Health risks to users from smoke agents are predominantly respiratory, with zinc chloride inhalation causing acute symptoms such as coughing, dyspnea, and inflammation, potentially leading to severe conditions like adult respiratory distress syndrome (ARDS) even from brief exposures in training or combat.^[84] Long-term studies on military personnel indicate that repeated exposure to smoke obscurants may contribute to chronic respiratory issues, with some research linking multi-agent exposures—including particulates from smokes—during operations like the Gulf War to unexplained syndromes involving fatigue, joint pain, and persistent lung damage.^[85] Regulatory frameworks under the United Nations, particularly the CCW and its protocols, have increasingly addressed persistent smokes since the early 1990s, emphasizing restrictions on agents with prolonged environmental impacts to mitigate unnecessary suffering and ecological harm, though non-toxic obscurants remain permissible in limited tactical roles.^[86] These measures drive modern military applications toward safer, biodegradable formulations to balance operational needs with sustainability.

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