Long Ignored: The Use of Chemical and Biological Weapons Against Insurgents


A conventional shibboleth is that chemical and biological agents have no place in modern conflicts. In this view, chemical and biological agents are not useful because they are inhumane, uncontrollable, ineffective, or obsolete in the face of modern conventional weapons. These arguments were put forth when the U.S. decided to ban biological weapons, and later applied to chemical weapons. However, a review of chemical and biological weapons use since the end of World War I puts the lie to many of these claims. Chemical and biological agents possess significant utility in modern counterinsurgency campaigns, as Rhodesia and Syria have demonstrated. (One disclaimer is apropos at this point: This argument does not justify or condone the use of chemical or biological agents in any form or at any time unless legally sanctioned by the relevant international agreements.)

Throughout history, chemical and biological agents have demonstrated effectiveness against ill-equipped, ill-prepared, or poorly trained adversaries, especially insurgents. Examples of the use of these weapons against insurgents include Spain (Rif war, 1921-1927), Italy (1935-1936), Egypt (1963-1967), Rhodesia (mid-late 1970s), South Africa (1980s), Libya (1987), Iraq (1988), and Syria (2013-ongoing). And while the Spanish, Italian, Egyptian and Libyan uses are examples of the use of chemical weapons in inter-state conflict, most of the cases involve colonial governments using the weapons against native insurrections. The Rhodesian example illustrates a regime’s largely internal use of chemical and biological agents against insurgents. These are clear parallels between this example and Syria’s well-publicized use of chlorine and sarin against civilians, which has been ongoing since 2013.

As Chris Quillen points out, Arab nations used chemical weapons after conventional forces proved ineffective in the wake of prolonged conflict that strained economies, weakened international standing, and threatened vital assets. Quillen argues that chemical agents were used as a weapon of last resort and that therefore, these cases demonstrate the strength of the norms and taboos prohibiting the use of these weapons.

But a counterargument is that international norms are weakened with each consecutive use and the absence of an effective response. Richard Russell asserted in a 2005 article that “Nation-states are likely to learn from Saddam [Hussein] that chemical weapons are useful for waging war against nation-states ill-prepared to fight on a chemical battlefield as well as against internal insurgents and rebellious civilians.”

The conclusion from these examples is that regimes in extremis — when the battle is for their very survival — seem to have little compunction about resorting to chemical and biological weapons use. The much-heralded international norms and conventions prohibiting and condemning chemical and biological development and use go out the window when a regime’s survival is at stake. In academic and policy circles, the norms against chemical and biological development and use seem almost sacrosanct, inviolable. The Rhodesian case dispels the myth and offers a more nuanced understanding of the role the norms play and the circumstances in which those norms are abandoned. When regimes are fighting for survival and perceive that chemical or biological agents can help defeat an insurgency, the use of these weapons becomes more attractive despite the existence of norms. The examples of Rhodesia and Syria show that the international community must be united and demonstrate the requisite political will to enforce norms if the use of chemical and biological weapons is to be prevented.

The Rhodesian Case Study

The Rhodesian example is likely the only example of biological weapons use by a nation since the end of World War II. The case allows us to examine the rationale behind a decision not only to develop, but also to use, biological weapons agents. Rhodesia also sheds light on other post-World War II chemical weapons cases, such as Iraq’s, particularly against its Kurdish population, and Syria’s, against insurgents in its civil war.

The lesson of Rhodesia and Syria is that regimes are much more likely to use these unconventional agents against internal opposition (i.e., insurgents and rebellious populations) than against foreign state adversaries. The Rhodesian case demonstrates how a small, internationally isolated regime can develop effective chemical and biological agents undetected and use those agents with lethal effect against both internal and external guerrilla threats.

Rhodesia covertly established a rudimentary, small-scale chemical and biological program using readily available materials, equipment, and techniques. Starting in 1965, Rhodesia faced international sanctions and a blockade of supplies entering the country through Mozambique’s port of Beira. Salisbury depended on Portugal (until the 1974 coup) and South Africa for foreign support (which became increasingly sporadic after 1975). The loss of Portuguese support and the unpredictability of South African assistance led Rhodesia to turn to chemical and biological weapons as self-help.

Rhodesian decision-makers adopted an unconventional response to the growing imbalance that favored the far more numerous insurgents. After the collapse of Portuguese colonial power in Mozambique — along with the dramatic increase in guerrilla recruitments and the escalating violence — people within the security structure realized the counterinsurgency could not be won solely through the conventional military.

With scant material resources, the project employed relative novices in basic facilities to produce significant amounts of lethal material in a short period of time. The Rhodesian effort also shows that states, groups, or individuals lacking funds or sophisticated equipment can easily use toxic agricultural and industrial chemicals as chemical weapons agents. By minimizing reliance on foreign suppliers and limiting personnel to a small, tightly knit group, nations and non-state actors can reduce the likelihood of discovery by foreign intelligence services.

If the Rhodesian sources are credible, their chemical and biological effort at times inflicted more guerrilla casualties than the conventional military operations did. This comparative success was largely due to guerrilla hit-and-run tactics that emphasized avoiding contact with Rhodesian forces in favor of attacking softer civilian targets. In other words, where the Rhodesian military struggled to locate and engage an elusive foe, the chemical and biological effort sought to kill the guerrillas in their camps and bases, and among their village supporters. These attributes made chemical and biological warfare well-suited to counterinsurgency when the regime’s aim was survival.

The lessons of the Rhodesian chemical and biological program and its legacy are more relevant today than is commonly realized. Outside the international system — and already under crushing sanctions — Rhodesia had very little to lose in adopting chemical and biological agents. International opprobrium would have had little effect on Rhodesian decision-making. Second, little global attention was focused on events inside Rhodesia. What little attention Rhodesia did get myopically monitored Soviet and Chinese support for the insurgent parties, who were widely seen as Marxist proxies. The covert nature of the Rhodesian program compounded the lack of attention. Western diplomatic, intelligence, and journalistic channels did not report the Rhodesian production and use of chemical and biological agents, despite ineffective insurgent efforts to raise awareness of the issue.

International norms against chemical and biological weapons had no impact on Rhodesia’s decision to use these agents. Although the regime was aware of treaty obligations, no evidence exists to suggest that Rhodesian authorities even debated the reaction of the international community when they established their chemical and biological weapons effort. As a footnote, the British government deposited a reservation to the Biological Weapons and Toxins Convention in March 1975 stating that the U.K. could not be held liable for any breach of the convention that might occur in Rhodesia while the colony remained beyond British control. The Soviet Union promptly protested the British reservation. Clearly, authorities in London wanted to avoid blame for any Rhodesian violations of the Biological Weapons and Toxins Convention, while Moscow sought to hold the U.K. culpable for acts by the rebellious Rhodesians. In either case, the outlaw Rhodesians actually involved in biological weapons use were beyond the pale of international obligation. The Rhodesians believed using these agents against the counterinsurgency was necessary to preserve their regime and way of life regardless of international law.

The Syrian Example

Like the Iraqi chemical weapons program, Syria’s interest in chemical weapons began after the Egyptian use in Yemen in the 1960s. However, Damascus did not adopt a full-fledged chemical weapons program until its military inferiority was unmasked by the 1982 Israeli invasion of Lebanon. The sense of inferiority — and the perceived unwillingness of Arab neighbors to rise to Syria’s aid — resulted in Damascus’ adoption of chemical weapons by the mid-1980s. Chemical weapons were the most expedient means of protecting the Assad regime from catastrophic defeat at Israeli hands. Similarly, the Rhodesian chemical and biological effort began out of an increasing awareness of the deteriorating security situation in the face of international isolation.

Even though Damascus’s interest in chemical weapons first arose in an international/regional context focused on deterring Israel, the utility of the weapons for the Syrian regime has been, like Rhodesia, in countering its internal insurgency. The Syrian attack on Khan Sheikhoun demonstrates the utility of chemical weapons in the counterinsurgency. According to the declassified assessment by the U.S. intelligence community, released on April 11, 2017:

The Syrian regime maintains the capability and intent to use chemical weapons against the opposition to prevent the loss of territory deemed critical to its survival. We assess that Damascus launched this chemical attack in response to an opposition offensive in northern Hamah Province that threatened key infrastructure.

On the same day, a senior U.S. official elaborated on the threat posed by the rebel offensive in Hamah. The official stated:

The regime we think calculated that with its manpower spread quite thin, trying to support both defensive operations and consolidation operations in Aleppo and along that north-south spine of western Syria, and also trying to support operations which required it to send manpower and resources east toward Palmyra, we believe that the regime probably calculated at that point that chemical weapons were necessary in order to try to make up for the manpower deficiency.

These assessments clearly illustrate that Damascus resorted to the use of chemical weapons to compensate for inadequate conventional military resources as it sought to counter an imminent threat to a key population center and a vital air base. The U.S. intelligence assessment even emphasized these regime assets as “critical to its survival.”

Effective Constraints on Chemical And Biological Use

Although a prevailing assumption has held that chemical and biological weapons will not be used because of a combination of ineffectiveness, international norms, and international agreements, Rhodesia and Syria show that this perspective doesn’t tell the full story. Deterrence (i.e., the credible threat of military action) likely is the only effective means of preventing the use of these weapons. International agreements and prohibitive international norms or taboos are largely ineffective unless the political will exists to punish the transgressor. Prohibitions against chemical and biological weapons are enshrined in international agreements, most notably the Biological Weapons and Toxins Convention and the Chemical Weapons Convention. Yet these agreements have been ineffective in constraining the production and use of these agents.

The political will for action in the international community has also long been severely lacking — witness the inaction after the gassing in Halabja and President Obama’s “red line” in Syria. After the Obama administration ultimately decided against striking Syria in 2013, the Kerry-Lavrov agreement resulted in Damascus’ accession to the Chemical Weapon Convention and its surrender of declared chemical weapons stocks for destruction. Yet as later events demonstrated, Syria retained chemical weapons materials and remained willing to use them against civilians, making the ultimate value of the Kerry-Lavrov agreement questionable.

Despite the conventions, several state parties to these agreements likely have chemical and/or biological weapons programs. A number of states have maintained biological weapons programs in contravention to the Biological Weapons Convention, as demonstrated by the well-known example of Yeltsin’s termination of the Soviet program in 1992. Another party to the convention, South Africa, developed and used biological weapons agents for over a decade after ratifying the agreement. Although the Chemical Weapons Convention now has been in force for 20 years, several signatories likely still possess chemical weapons. According to a June 2017 fact sheet assembled by the Arms Control Association, convention signatories thought to possibly retain covert chemical agents or munitions include China, Iran, Israel, North Korea, Russia, and Syria.

The apparent lack of international political will to confront the use of chemical and biological weapons should be evidence that the norms and taboos against the production, possession, and use of these weapons have eroded. Those norms and taboos represent the prevailing international consensus — embodied in international agreements — that underpins the political will to action. Norms represent a consensus defining appropriate and inappropriate conduct by nation-states under anarchic conditions. Norms are not universal nor are they immutable.

Taboos, on the other hand, are prohibitions on conduct considered so morally repugnant and reprehensible so as to be universally condemned. Following the experiences of World War I, chemical and biological weapons became taboo. But even so, World War II saw a massive increase in the number of national chemical and biological programs. Arguably, Allied and Axis powers were deterred from using these weapons by fear of retaliation from the opposing side.

Yet the Axis powers used chemical and biological agents on an enormous scale against vulnerable populations. Japanese units using weapons developed by Unit 731 wrought untold destruction on Chinese military units and civilian communities. For his part, Adolf Hitler may have prohibited use of chemical and biological agents against Allied forces, yet he was not dissuaded from using poison gas (Zyklon B) against millions of civilians. In neither of these instances was the taboo effective. The effect of deterrence and the relevance of international norms in preventing chemical and biological weapons use is arguably lessened when a nation-state is facing an ill-prepared or vulnerable population. The Arab, Rhodesian, and South African cases all bear this out.

Syria’s recent use of chemical weapons likely has diminished effectiveness of the chemical and biological prohibitions, as have previous uses (i.e., Egypt, Libya, and Iraq). The international community’s failure to act more decisively may embolden other marginal nations to explore chemical and biological adoption and use to counter threats to their internal security.

Although the U.S. cruise missile strike on April 6, 2017, against Syria’s Shayrat airfield signalled Washington’s resolve to punish Damascus for future chemical weapons use, the political impact (and legality) of the U.S. strike remains debatable, especially given allegations of continued Syrian use. According to an article in the German paper Die Welt in July 2017, “Western intelligence agencies confirmed to Die Welt that Syria’s government continues to use poison gas against its own population. Apparently, the regime understands the latest signals from the U.S. as an encouragement.” As of early June 2017, the U.S. government itself warned of a possibly imminent Syria chemical weapons attack, further suggesting the attack on Shayrat failed to sufficiently punish the Assad regime.

One reason the U.S. strike may not have prevented further use is that it came from the U.S. alone. Unilateral action against the transgressor demonstrated the weakness of the norm in that the international community lacked the political will to act. The absence of political will is highlighted by Russia’s repeated vetoes of U.N. resolutions condemning Syria for its chemical weapons use. Furthermore, a member of the U.N.’s war crimes commission, Carla Del Ponte, resigned in early August 2017, saying, “The Assad government has perpetrated horrible crimes against humanity and used chemical weapons…I am quitting this commission, which is not backed by any political will. I have no power as long as the [U.N.] Security Council does nothing. There is no justice for Syria.”

The Bottom Line

Despite the international moratorium on chemical weapons use in interstate conflict, these agents are effective in suppressing internal violence. Chemical and biological weapons’ lack of utility against well-prepared, well-equipped adversaries deters their use against modern militaries, yet historically the weapons have been effective against the unprepared or vulnerable.

The post-World War II examples of chemical weapons use show that their greatest utility is in intrastate counterinsurgency operations and in attacks on ill-prepared and poorly equipped or trained adversaries. This perceived advantage is likely the greatest obstacle to the elimination of these arms from national arsenals. As demonstrated in Rhodesia, Iraq, and Syria, the norm against chemical and biological weapons use is weakest in low-intensity counterinsurgencies involving rogue or pariah regimes, and when poisons and toxins are used in special operations and assassinations (examples include Chile under Pinochet, South Africa, and Russia). The Rhodesian and Syrian cases clearly show the relative inability of international norms to prevent the use of chemical and biological weapons in these cases. For norms to be truly effective, there must be unanimity among nations about enforcing the prohibitions. As we’ve seen in Syria, such consensus is elusive, and the international community has failed to act. As a consequence, the world faces a sad, but inevitable conclusion. The Syrian regime is unlikely to ever face justice for its use of chemical weapons.


Glenn Cross is the author of the recent book, “Dirty War: Rhodesia and Chemical, Biological Warfare.” He has served for 29 years in the Intelligence Community as a CIA analyst, manager of biological weapons analysts in the FBI, and in the ODNI as the deputy NIO for WMD, responsible for IC’s biological weapons analysis from 2008 to 2010. Dr. Cross holds an AB from Columbia University, an MA from King’s College, London in War Studies, a second MA (with distinction) from George Mason University, and a PhD from George Mason’s Graduate School of Science in Biodefense, where the former deputy head of the Soviet biological weapons program, Ken Alibek, was his dissertation advisor. Dr. Cross went on to do a postdoctoral fellowship at Georgetown University Medical School developing means for attributing biological weapons attacks. Views and opinions expressed here are solely those of the author and do not represent the positions or policies of the US government.

Image: U.S. Navy photo by Journalist 3rd Class Stephen P. Weaver