The Dark Side of the Chemical Weapons Convention: Case Studies in Urban Warfare

The Dark Side of the Chemical Weapons Convention: Case Studies in Urban Warfare

By Ryan N. Mannina 

Introduction

Does humanitarianism have a dark side? International humanitarian law (IHL) is devised with the ostensible aim of advancing humanitarian interests; that is, to constrain the use of force in war in order to save human lives and alleviate suffering. Yet, even dedicated humanitarians acknowledge that they are often better at devising new law than at assessing the performance of existing accords.[1] Such an assessment is both worthwhile and necessary. This article examines how IHL performs in an urban warfare context. This is an important question because, as the world rapidly urbanizes, there is an increasing sense of urgency in the U.S. Army to study urban warfare and consider how it might be fought in the future. In addition to considering how the Army should prepare itself, policymakers need to think about how national policy and IHL contribute to the military’s success in urban warfare.

Existing humanitarian law was largely influenced by—and designed for—the wars of the nineteenth and twentieth centuries. How will these treaties perform in the changing context of twenty-first century warfare? In the past two decades, the United States and its allies have fought several destructive urban battles to liberate cities like Fallujah, Mosul, and Raqqa from armed nonstate groups. These battles resulted in large numbers of noncombatant casualties and left vast areas of the urban landscape uninhabitable. Urban warfare imposes high costs in lives, political capital, and national treasure. The Battle of Mosul alone displaced more than 826,000 Iraqi citizens and destroyed over 40,000 homes. The cost of rebuilding Iraq after the campaign to eject the Islamic State will cost more than $88 billion.[2] These costs can make policymakers and military leaders hesitant to undertake such operations, thereby restricting military options in war. Identifying less destructive methods could allow the military to wage urban warfare more humanely and reduce the associated costs.

This article contributes to the study of urban warfare by examining the implications of the United States’ membership in the Chemical Weapons Convention. It asks whether the CWC’s prohibition of riot control agents (RCAs) as a method of warfare has saved human lives and alleviated suffering in urban warfare. The answer, unfortunately, is that the prohibition has caused the military to adopt alternative weapons and tactics that are more lethal and less discriminate than riot control agents, and thus cause greater collateral damage and human suffering in urban warfare.

A comparative analysis of the Battle of Hue (1968) and the Second Battle of Fallujah (2004) allows us to examine variations in the types of weapons and tactics that U.S. forces employed during urban combat before and after the prohibition of RCAs. In both cases, the unique characteristics of urban terrain often advantaged the defender and limited the attacker’s maneuver. The Marines in Hue relied heavily on CS, a form of concentrated tear gas, to provide freedom of maneuver. The use of CS reduced the need to employ high explosive munitions—which are inherently indiscriminate—delivered by aircraft and artillery, and provided a nonlethal option for escalation of force that undoubtedly prevented unnecessary civilian deaths.

In contrast, U.S. forces did not use RCAs during the battle of Fallujah. Due to the prohibition established in the CWC, they lacked a nonlethal method of escalation when they found themselves unable to maneuver. They relied instead on high explosive munitions delivered by tanks, artillery, mortars, and air support, often destroying entire buildings to suppress or destroy a single enemy sniper.[3] In some instances, U.S. forces allegedly forced insurgents out of their fighting positions by employing the toxic and caustic properties of white phosphorus smoke. Some consider this a flagrant violation of the CWC.[4] Yet, perversely, it is the CWC’s prohibition of RCAs that served to bring about this adaptation.

The Battle of Hue (31 January – 3 March 1968)

            In 1968, Hue was a modern European-style city with a population of 140,000.[5] It was located on the Huong River, a major waterway that bisected the city. The majority of the city was inside the Citadel, a stone fortress constructed by the French during the nineteenth century that was situated on the north bank of the river. The Citadel dominated the southern portion of Hue, which was an area nearly as large and spread along the river’s south bank.[6]

On 31 January 1968, more than fourteen battalions of North Vietnamese Army (NVA) and Viet Cong (VC) attacked to seize the city, which was only lightly defended by U.S. and Army of the Republic of Vietnam (ARVN) forces.[7] The attackers seized most of the city within the first few hours. On 1 February, U.S. and ARVN units began fighting to recapture the city.[8] ARVN forces were responsible for clearing the Citadel, while U.S. Marines were responsible for the southern portion of the city.[9] The Marines successfully cleared and secured the southern portion of the city by 10 February, then assisted ARVN forces in clearing the Citadel.[10] They declared the city secure on the morning of 25 February, although clearing operations continued until 2 March.[11] U.S. and ARVN casualties were 637 killed, 3,732 wounded, with North Vietnamese casualties between 2,500 and 5,000.[12]

Map 1. Operation HUE CITY: Battle of Hue, February 1968

Map source: Villard, Staying the Course, 417.

The majority of the Marines who fought in Hue had no previous experience with the type of large-scale urban combat they encountered.[13] They learned quickly that some characteristics of the urban environment provided significant advantages to the defending forces. The Citadel was a densely populated area with heavy stone and masonry buildings in close proximity to one another.[14] The streets were narrow, and most of the structures were separated by high walls or hedgerows laced with barbed wire and embedded with broken glass and other sharp objects.[15] In the southern portion of the city, the structures were not as closely spaced and the streets were wider. Most houses were made of softer material than those in the Citadel and were thus easier to breach.[16] The presence of civilians was another important feature of the battlefield. Although Hue’s population was “essentially passive,” the Viet Cong forced them to assist in a variety of ways such as carrying wounded and supplies, and digging fortifications.[17] The NVA used nearby villages to manage resupply, medical evacuation, and prisoner of war processing and detention.[18]

The NVA were adept at fortifying and camouflaging themselves in Hue’s urban terrain. They created strong points in multi-floor buildings surrounded by courtyards. They placed snipers in the upper floors and automatic weapons in the lower floors. Foxholes surrounded the courtyards, each manned by an NVA soldier equipped with an assault rifle and rocket launcher. The city’s treasury was strongly fortified.[19] The urban terrain provided several advantages to the defending force. First, buildings provided cover and concealment from aerial and ground reconnaissance, as well as direct and indirect fire weapon systems. Second, narrow streets lined with linear obstacles canalized the movements of the attacking forces along a limited number of avenues of approach and made enemy positions difficult to breach. Third, elevated positions, such as rooftops and upper story windows, provided defenders excellent observation and fields of fire as attackers moved through the city. Fourth, the desire to spare civilian lives and infrastructure led to restrictive rules of engagement on the U.S. side. Finally, the NVA’s use of neighboring villages for combat service support highlights the difficulty of isolating a city and cutting off support to the defending forces.

The 1^st Marine Division’s after action report discussed special equipment and techniques that involved extensive use of CS gas, also known as tear gas.[20] CS gas causes irritation to the eyes, nose, and throat and—in sufficiently high concentration—incapacitation due to the inability to see and preoccupation with the agent’s effects.[21] The Marines used the E8 launcher and 35mm Tactical CS Cartridge to “break strong points or soften enemy positions prior to an assault.”[22] Because it relied on the infiltration of gas from outside the building, the E8 launcher was often ineffective against buildings with few openings or those with high, solid walls surrounding them. In these instances, Marines employed the M630 mortar CS cartridge.[23] The M630 cartridge could penetrate the tile roofs typical of Hue’s buildings, which allowed the gas to be fully concentrated inside the building.[24] A third technique was the use of CS gas grenades. These provided an important nonlethal escalation option, especially when clearing bunkers and buildings where civilians might be present. The Marines would often throw the grenades into structures in an attempt to force their occupants to surrender or flee before escalating to lethal munitions.[25]

The CS gas disorganized NVA soldiers who had fortified themselves in urban structures, and allowed assaulting Marines to seize their objectives with fewer casualties.[26] CS was critical for 1^st Battalion, 5^th Marines as they cleared the dense urban terrain inside the Citadel. The battalion began its assault on the Citadel on 13 February. After two weeks of heavy street fighting, it had secured only sixteen city blocks while suffering nearly 50% casualties. On 25-26 February, by employing E8-launched tear gas canisters, they cleared the remaining twelve city blocks without taking a single casualty.[27] Noting that the NVA were not equipped to withstand a tear gas attack, officers lamented the fact that they had been unable to employ tear gas earlier in the battle, and recommended “the judicious use of chemical weapons, such as tear gas, etc. for [future] urban combat operations.”[28]

Certainly, the Marines also relied heavily on lethal munitions to suppress the enemy and provide freedom of maneuver. Air support played a decisive role at key points, but adverse weather conditions often limited the employment and effectiveness of both fixed-wing and rotary-wing aircraft.[29] Due to the desire to avoid unnecessary damage to civilian structures, the rules of engagement restricted the use of heavy artillery in the early stages of the battle. This restriction was eased in the later stages as the Marines’ casualties mounted and the strength of the enemy force within the city became clearer.[30] Throughout the battle, they employed 5,304 rounds of naval gunfire, more than 235,000 pounds of ordnance from 85 fixed-wing close air support sorties, 30 helicopter gunship missions, and countless mortar and artillery rounds.[31]

Three challenges emerged regarding artillery employment in the urban environment. First, most fire missions targeted enemy positions one hundred meters or less from friendly forces.[32] The U.S. military describes such missions as “danger-close,” indicating increased risk to friendly troops.[33] In some cases, the distance between friendly and enemy troops was too close to allow the use of artillery.[34] Second, the NVA used civilians as human shields, forcing Marines to account for increased risk to noncombatants.[35] Third, due to the low-angle trajectory of artillery fire, its effectiveness was often limited by the height of buildings and their close proximity to each other. In such cases, the Marines preferred to use mortars because their high-angle trajectory allows them to be fired over and in between buildings with greater precision and accuracy.[36]

Figure 1. Artillery and Mortar Dead Space in Urban Terrain

Image adapted from Department of the Army, FM 3-90.2, Figure 7-7.

Another tactic, called “mouse-holing,” allowed Marines to minimize their exposure to enemy observation and fire while moving through the urban environment. They blew holes in the sides of buildings (mouse holes) with satchel charges, rockets, tank cannons, or recoilless rifles, and used them to move between and through buildings without exposing themselves to enemy observation and fire.[37] Heavy weapons like tanks and recoilless rifles provided the added benefit of shocking defenders inside buildings and rendering them temporarily less capable of defending their positions.

Officers from the 1^st Infantry Division Advisory Detachment summed up the humanitarian costs of the battle in an after-action report: “The City of Hue is virtually in ruins. Refugees and homeless from the civilian population, the civilian wounded, the enemy dead, and the lack of utilities present a serious problem.”[38] Approximately 80% of the houses inside the Citadel were completely destroyed during the battle.[39]

Despite the extensive destruction, noncombatant deaths due to collateral damage appear to have been relatively low. Estimates of the number of civilians killed during the battle vary between 4,000 and 7,000.[40] The South Vietnamese government estimated 7,600 total casualties. Of those, they attributed 1,900 wounded and 944 deaths to “accident of battle,” or collateral damage. Other sources put that number at 1,200.[41] In total, collateral damage resulted in civilian mortality rates between 7:1,000 and 9:1,000. Widespread destruction left about 115,000 of the city’s residents temporarily homeless.[42] An ARVN colonel later described the psychological trauma suffered by countless more caused by shortages of food and water, not to mention living “among decaying corpses that could not be buried and whose stink could drive everyone to hysteria.”[43] These statistics and accounts illustrate one of the most significant characteristics of urban warfare: civilian death and suffering are unavoidable consequences of war in such environments.

The Second Battle of Fallujah (November – December 2004)

Fallujah, Iraq was the setting of two major battles between the U.S.-led coalition and Iraqi insurgents in 2004. The city had a land area of approximately 21 square kilometers and a population of about 250,000 people. The U.S. military had easily occupied Fallujah soon after the invasion of Iraq in March 2003, but resistance to the occupation grew in Sunni-dominated areas of the country over the following year. In April 2004, the coalition launched the first battle of Fallujah, Operation Vigilant Resolve, in response to the ambush and mutilation of four U.S. private military contractors by Sunni militants.[44] After only two days of fighting, coalition forces withdrew from the city under pressure from Arab media outlets and Sunni politicians resulting from high levels of collateral damage.[45]

Fallujah became an insurgent stronghold in the following months. Insurgents immediately began violating the ceasefire by attacking U.S. and coalition troops. By forcing the coalition to abandon its assault on the city, the insurgents gained a valuable propaganda and recruiting narrative that drew thousands more insurgents from all over the country, as well as foreign fighters from outside of Iraq. By October, the coalition estimated that 4,500 insurgents had occupied the city. In order to facilitate upcoming national elections, coalition leadership decided to assault the city for a second time to clear it of insurgents.[46]

The second battle was a three-phase operation named Operation Al Fajr (“New Dawn” in Arabic). In the first phase, the coalition prepared the battlefield by employing air strikes, special operations raids, and psychological and information operations to confuse the insurgents and kill key leaders. This phase also included leaflet drops and radio broadcasts warning Fallujah’s civilian population to evacuate the city. In the second phase, U.S. forces isolated Fallujah by seizing key ingress and egress routes, jamming communications, and cutting off the city’s electricity. The third phase was the actual assault on the city.[47]

The attacking force comprised two Marine Regimental Combat Teams (RCT), RCT 1 and RCT 7. Each was reinforced with one U.S. Army battalion: 2^nd Battalion, 7^th Cavalry Regiment, and 2^nd Battalion, 2^nd Infantry Regiment, respectively. In addition, six Iraqi battalions participated in the operation. The coalition began its assault on November 8 and defeated all organized resistance by November 13, although fighting continued for several weeks as the coalition cleared small cells of insurgents in sustained search and attack missions.[48] U.S. forces suffered 63 killed and more than 600 wounded. Coalition troops reported 2,175 insurgents killed and 2,052 captured.[49]

Map 2. Operation AL FAJR: Second Battle of Fallujah, November 2004

Map source: Rayburn, The U.S. Army in Iraq, 350.

            In 1975, the United States ratified the 1925 Geneva Protocol, which prohibited “the use in war of asphyxiating, poisonous or other gases, and of analogous liquids, materials or devices.”[50] Although he ratified the treaty, President Gerald Ford issued Executive Order 11850, which reserved the United States’ right to use RCAs in specific circumstances.[51] The United States later signed and ratified the CWC, which entered into force in 1997. The CWC prohibits the use of chemical weapons in any circumstances. It further prohibits the use of RCAs—defined as “any chemical… which can produce rapidly in humans sensory irritation or disabling physical effects which disappear within a short time following termination of exposure”—as a method of warfare.[52]

When it ratified the CWC, the U.S. Senate specified that E.O. 11850 would remain in effect as the primary document governing the United States’ use of RCAs.[53] Apparently relying on the language of the Executive Order, President George W. Bush authorized the U.S. military to use RCAs in Iraq under “specific, well-defined circumstances.”[54] Those well-defined circumstances refer to four defensive scenarios outlined in E.O. 11850. Since Al Fajr was an offensive operation, it was not covered by E.O. 11850 and coalition forces were not armed with RCAs during the battle.

The Urban Environment

            The urban environment in Fallujah resembled that of Hue in many ways. The streets were narrow and generally lined by walls. The urban terrain was dense, with structures generally built so close together that they were touching, or nearly so. This canalized troops as they moved through the city and restricted their maneuver. The houses were typically surrounded by enclosed courtyards, which were in turn overlooked by rooftops and upper story windows and provided insurgents with excellent observation and fields of fire. Houses were generally constructed of brick, and their roofs were made of thick mortar, which provided cover and concealment from small arms and explosives. Exterior doors were usually metal or wood, with a metal gate on the exterior and several locking points, making them especially difficult to breach.[55]

As in Hue, the advantage in this urban environment often went to the defenders. Once again, U.S. forces found that the urban terrain necessitated special adaptations in weapons and tactics. Unlike in Hue, however, troops in Fallujah did not have access to RCAs. Whereas the Marines in Hue used CS gas to force enemy soldiers out of fortified buildings, troops in Fallujah often resorted to more lethal and destructive means.

Weapons and Tactics

Coalition troops relied heavily on artillery, mortars, and air support. They employed 386 close air support strikes and more than 14,000 artillery and mortar rounds throughout the battle.[56] One significant advancement since the battle of Hue was the advent of precision-guided munitions (PGMs) and advanced targeting systems. By 2004, the U.S. military had developed a multitude of air-delivered PGMs. For target location and identification, U.S. forces used hand-held and vehicle-mounted laser target designators and rangefinders that could mark targets or provide exact GPS coordinates once a target was identified.[57] The PGMs used in Fallujah were predominantly either laser-guided or GPS-guided. Laser guidance relies on an observer to mark the target with a laser designator system. The bomb’s onboard electronics then track the laser’s energy and guide the bomb onto the target.[58] GPS guidance relies on the observer or aircrew loading accurate GPS coordinates to the target into the bomb’s navigation control system. Table 1 depicts the characteristics of some of the PGMs most commonly used in Fallujah.[59]

Table 1. Risk Estimate Distances for Precision-Guided Munitions Commonly Used in Fallujah

              Because of the widespread employment of PGMs, Fallujah was hailed as a military operation of unprecedented precision. However, there are a variety of factors that affect precision. One typical measure of a bomb’s precision is 50% circular error probable (CEP). CEP describes “the radius of a circle around the target within which 50% of the weapons should fall. The remaining 50% fall outside the CEP.”[60] In 2003, the JDAM’s published CEP was “5 meters or less during free flight when GPS data is available.”[61] In other words, 50% of JDAMs could fall more than 15 feet off-target under ideal conditions. In dense urban terrain, where buildings are often touching, or nearly so, that can result in bombs destroying the wrong buildings and killing or seriously injuring any noncombatants caught inside. Other sources of error include atmospheric conditions, pilot proficiency, and target location error.[62]

Furthermore, the data in Table 1 demonstrate that even when a bomb impacts exactly where intended, there is a high risk of collateral damage to anyone standing nearby due to blast overpressure and fragmentation. For example, there is a 10% probability that a soldier standing within 50 meters of a target hit by a GBU-12 would be incapacitated.[63] Structures in the urban environment mitigate some of the risk by absorbing the bomb’s effects; however, overpressure can also cause buildings to collapse dozens of meters from the point of impact. Unreinforced masonry buildings like those found in Fallujah are the most vulnerable to collapse from blast overpressure.[64] Therefore, it is clear that bombs, no matter how accurate and precise, are inherently indiscriminate.

            Despite the heavy reliance on indirect fire and air support, their utility remained limited in some situations. Fixed-wing close air support could take too long and was often judged too dangerous to be employed in the close quarters fighting that characterized the battle.[65] Artillery and mortars were much more responsive. Troops often preferred to use mortars due to their high angle of trajectory. However, their high trajectory sometimes endangered supporting aircraft, thereby restricting their employment.[66]

Due to limitations of indirect fire and air support, infantry troops in Fallujah often found the heavy firepower provided by tanks and combined anti-armor teams (CAAT) more effective for dealing with insurgents fighting from fortified buildings. Marines used the Abrams tank’s 120mm cannon to neutralize enemy snipers and the CAAT’s .50 caliber machine guns and Mk19 grenade launchers to destroy buildings that the insurgents were using as fighting positions.[67] The Army relied perhaps even more heavily on combined arms teams. “Soldiers did not hesitate to level a building from which they received hostile fire before they occupied it. With only a few exceptions, they also did not hesitate to destroy buildings simply suspected of holding insurgents.”[68] While necessary to facilitate movement and maneuver in the city, these tactics were inherently indiscriminate.

The employment of white phosphorus (WP) munitions became a point of major controversy.[69] White phosphorus is an incendiary and toxic chemical that burns when exposed to air at certain temperatures. It glows in the dark and produces white smoke when burned, making it a versatile munition.[70] It can be used as an antipersonnel weapon, or for obscuring the movement of friendly troops, illuminating the battlefield, signaling, or marking targets.

According to the OPCW, the CWC forbids the use of white phosphorus if the chemical’s toxic or caustic properties are “specifically intended to be used as a weapon.”[71] Therefore, the United States has officially rejected the use of white phosphorus as an antipersonnel weapon since the entry into force of the CWC.[72] Nevertheless, the Army and Marines used white phosphorus extensively in Fallujah. U.S. officials denied that it was used as a chemical weapon, but soldiers and Marines provided accounts that cast doubt on those claims.[73] One artillery officer described using white phosphorus as a psychological weapon against dug-in insurgents: “We fired ‘shake and bake’ missions at the insurgents, using WP to flush them out and [high explosive munitions] to take them out.’”[74] A Marine described using improvised bombs made from white phosphorus mortar rounds to force insurgents out of fortified buildings.[75]

If these methods relied primarily on the toxicity of the white phosphorus smoke, then white phosphorus essentially served as a substitute for nonlethal chemical munitions like the CS gas used in Hue and might have been interpreted as a violation of the CWC. However, unlike CS gas, white phosphorus has lethal effects. It sets fire to any combustible material with which it comes into contact, causing secondary fires and additional property destruction. Acute white phosphorus exposure causes systemic toxicity in humans that can result in death.[76]

As in the battle of Hue, it is difficult to find reliable data on the number of civilians killed as a result of collateral damage in Fallujah. Around 80% of the population evacuated Fallujah prior to the assault, leaving between 30,000-50,000 remaining in the city.[77] Of those, about 800 died during the battle.[78] Those numbers indicate a mortality rate between 16:1,000 and 26:1,000.[79] There is no data available on the number of civilians injured during the battle. Up to 40% of the buildings and homes in Fallujah were completely destroyed, while the rest sustained “significant” or “major” damage.[80] The battle left up to 200,000 residents temporarily homeless, and only 30% had returned to the city by March 2005.[81] In 2010, researchers found that residents experienced increases in birth defects, infant deaths, and cancer following the battle, as well as a “remarkable reduction in the sex ratio” in the cohort born one year later.[82] Researchers attributed those effects to environmental contamination, and speculated that it may have been caused by depleted uranium found in certain munitions employed by the U.S. military. Others suspected they may have been due to white phosphorus exposure.[83]

Based on the two case studies presented above, what generalizations can we make about military necessity in urban warfare? The DoD defines military necessity as “the principle that justifies the use of all measures needed to defeat the enemy as quickly and efficiently as possible that are not prohibited by the law of war.”[84] In both Hue and Fallujah, the urban terrain was itself the military objective. In order to defeat the enemy, U.S. and partner forces had to clear the cities of enemy fighters. However, the urban terrain advantaged the defenders in both cases. The myriad challenges of the urban environment presented a constant dilemma for U.S. forces. They had to figure out how to defeat enemy forces as quickly and efficiently as possible, while suffering as few casualties and causing as little collateral damage as possible. These two goals are more directly opposed in urban combat than any other kind. In both cases, U.S. forces employed destructive firepower to achieve freedom of maneuver. In Hue, however, they had another nonlethal option for escalation. They used CS gas extensively to overcome the military advantage that the urban terrain provided enemy fighters in the defense.

Table 2 shows a comparison between the casualty rates for civilians in Hue and Fallujah as a result of collateral damage. While the battle caused extensive destruction in Hue, RCAs almost certainly reduced civilian casualties. By prohibiting the use of RCAs as a method of warfare, the CWC caused military forces to resort to more destructive means of achieving their military objectives. In Fallujah, U.S. troops employed artillery, mortars, and close air support more heavily and caused massive collateral damage, notwithstanding advancements in precision-guided munitions. Additionally, they allegedly used the toxic properties of white phosphorus to force enemy fighters out of their fighting positions, essentially the same tactical effect achieved through the use of RCAs in Hue but with far more lethal and destructive effects on combatants and the urban environment.

Table 2. Battle Damage Statistics

The data in Table 2 illustrate that U.S. forces caused nearly as many civilian casualties during the six-day battle in Fallujah (800) as they did over the course of 25 days in Hue (944-1,200). This is despite the fact that the vast majority of Fallujah’s civilian population had evacuated the city prior to the battle, a luxury not afforded to the residents of Hue. In fact, when accounting for relative population size, the civilian mortality rate was between two and four times higher in Fallujah. Had noncombatants not had the opportunity to evacuate Fallujah prior to the battle, civilian casualties would have been much higher still.

In terms of physical destruction, Fallujah appears at first to have been fought more discriminately than Hue. Only about 40% of Fallujah was completely destroyed, while Hue suffered more extensive destruction of nearly 80%. Some have praised the precision and discrimination displayed through the use of “surgical air strikes” and precision-guided munitions in Fallujah.[85] However, it might be more appropriate to attribute the relatively moderate physical destruction to the lower density of enemy fighters occupying Fallujah (238/km²) as compared to Hue (384/km²). In absolute terms, the destruction of Fallujah was almost certainly more extensive; between 7,000-10,000 of the city’s 50,000 homes were completely destroyed, as many as two homes for every enemy fighter in the city.[86] In terms of displaced persons, a similar percentage of residents were left homeless in both cities: up to 82% in Hue, and up to 80% in Fallujah. These numbers defy the notion that the precision afforded by PGMs is an adequate substitute for the discrimination afforded by RCAs.

            When it comes to the use of RCAs in urban warfare, military necessity and humanitarian interests overlap. On the urban battlefield, military necessity dictates that troops must find a way to maneuver freely through cities from a position of great disadvantage. In both Fallujah and Hue, U.S. forces often did this by destroying occupied structures with high explosives, but the lack of a nonlethal alternative in Fallujah meant that they resorted to destructive tactics more quickly and more frequently. Furthermore, it probably led U.S forces to adapt a lethal munition—white phosphorus—to achieve tactical effects that might otherwise have been achieved with nonlethal RCAs. Before their prohibition, RCAs employed this way certainly mitigated humanitarian costs in urban combat. This convergence of military necessity and humanitarian interests demonstrates that there is a role for RCAs that policymakers, military leaders, and humanitarians have a duty to consider when contemplating the future of urban warfare and the laws that govern it.

Policy Implications

            If the prohibition of riot control agents does indirect harm in the context of urban warfare, the trend toward increased levels of destruction and civilian casualties will continue as the world continues to urbanize. Recent urban battles seem to confirm that forecast. In the nine-month battle to liberate Mosul from the Islamic State, the U.S.-led coalition killed at least 3,200 civilians with airstrikes, artillery, and mortar fire.[87] This level of human suffering demands that policymakers and military leaders take action to render urban warfare more humane.

The United States must take action to revise the CWC’s prohibition against the use of RCAs as a method of warfare and reintroduce RCAs into the military’s arsenal. Executive Order (E.O.) 11850 reserves the United States’ right to use RCAs “in defensive military modes to save lives,” including four specified situations:

(a) Use of [RCAs] in riot control situations in areas under direct and distinct U.S. military control, to include controlling rioting prisoners of war.

(b) Use of [RCAs] in situations in which civilians are used to mask or screen attacks and civilian casualties can be reduced or avoided.

(c) Use of [RCAs] in rescue missions in remotely isolated areas, of down aircrews and passengers, and escaping prisoners.

(d) Use of [RCAs] in rear echelon areas outside the zone of immediate combat to protect convoys from civil disturbances, terrorists and paramilitary organizations.[88]

Why is it permissible to use RCAs when civilians are used to mask or screen attacks, or against prisoners of war who have already been rendered hors de combat, but not against fortified enemy combatants using human shields in the defense?[89] The President should amend E.O. 11850 to reflect the changing context of modern war. The amendment should authorize the use of RCAs during military operations in urban terrain when civilians are being used to shield enemy combatants, or when it is difficult or impossible to discriminate between combatants and noncombatants. Such an order is likely to spark intense criticism from some in the international community, such as the Organisation for the Prohibition of Chemical Weapons (OPCW). However, the order itself would not violate the CWC, and would be an important first step in the process of revising current humanitarian norms.

Furthermore, the military should study how the use of RCAs can benefit both humanitarian interests and military necessity in an urban warfare context. This article provides a starting point, but should be expanded to include additional case studies. Researchers should also seek to incorporate quantitative methods to confirm or deny the findings in this paper. The U.S. Army War College, the Marine Corps War College, and the National Defense University would be ideal proponents for this research. DoD simulations centers could employ advanced modeling and simulation technologies to test whether the employment of RCAs might improve tactical effectiveness while reducing civilian deaths and collateral damage in densely populated urban terrain. Simulations should recreate historical urban battles and experiment with the use of RCAs as an alternative to artillery and air strikes. Researchers should compare simulated collateral damage and friendly casualties with the historical record to determine whether RCAs might have provided benefits on the battlefield.

If further research and simulations produce positive results, researchers and the military should widely publicize their findings and engage humanitarian organizations in an effort to attract support for an eventual amendment to the CWC. Passing an amendment requires the approval of a majority of the 193 states parties, with no states parties voting against. Furthermore, amendments must be considered by an Amendment Conference immediately following a regular session of the Conference of States Parties that takes place every five years.[90] The next regular session is scheduled for 2023, giving the United States two years to engage in the process of revising existing humanitarian norms surrounding RCAs. In the meantime, executive branch agencies should engage allies and partners around the world on this important topic. Ideally, the amendment would simply remove the prohibition of riot control agents as stated in Article 1, paragraph 5. However, member states may find reason to keep the prohibition and add some caveat that allows for the use of RCAs in urban warfare or when combatants and noncombatants are intermixed, rendering the appropriate level of discrimination impossible.

            There may be chemical agents other than CS gas that could be adapted to urban warfare, such as fentanyl. In 2002, the Russian military used a fentanyl derivative to end a hostage crisis at a theater in Moscow. Russian commandos freed 851 of the 979 hostages from a theater held by heavily armed Chechen terrorists. Russian authorities made a number of mistakes during the operation, including miscalculating the dosage required to neutralize the terrorists, which caused the deaths of 128 hostages.[91] The incident demonstrated that fentanyl gas is probably not ideal for law enforcement operations.

Nevertheless, fentanyl might be more appropriate in an urban warfare context that requires a different set of calculations regarding necessity and risk. Consider the incident during the battle of Mosul in 2017, when a U.S. airstrike killed more than 100 civilians taking shelter from the fighting in a residential neighborhood. Responding to a request for air support from Iraqi forces who were pinned down by sniper fire, the U.S. Air Force dropped a GBU-38 JDAM on the structure the snipers were occupying. The bomb impacted exactly where intended, but triggered a secondary explosion that caused the building to collapse and killed most of the civilians inside.[92] A mortar shell capable of releasing concentrated fentanyl gas might have neutralized the snipers without collapsing the building. More research is required to assess fentanyl’s potential use as a riot control agent.[93]

Conclusion

This article does not constitute unimpeachable evidence that the prohibition of riot control agents as a method of warfare is unequivocally harmful; nor does it intend to. Its purpose is to start a conversation about the potential unintended consequences of humanitarianism, and of the Chemical Weapons Convention in particular. The evidence presented herein simply illustrates the possibility that international humanitarian law, though written with the best of intentions, may not be capable of adapting at the speed of warfare. Treaties and conventions written in the 20^th century may have unforeseen and unintended consequences in 21^st century conflict. Too much is at stake in war to conduct it with blind faith in the laws that constrain its means. Cities are growing ever larger and more densely populated, and wars are more often being fought in cities. Humanitarians, policymakers, and military leaders thus have a duty to consider how international laws perform on the modern battlefield, and try to predict how they will perform in the future. Those that do not fulfill their intended purpose should be revised or discarded.

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