Biological Weapons in the ‘Shadow War’

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Do countries still need to worry about threats from biological weapons? The COVID-19 pandemic has led to renewed discussion of biological weapons and whether bad actors — both nations and terrorists — have refocused their attention on developing them. In a recent War on the Rocks article, Joseph Buccina, Dylan George, and Andy Weber argue that the “inadequate initial U.S. response to COVID-19, coupled with new advances in biotechnology, could make biological weapons more appealing for U.S. adversaries.” They add that China and Russia could use biological agents in a “low-boil” manner to undermine the United States as part of a “Shadow War,” a term first coined by Jim Sciutto, referring to a hybrid war, gray war, or non-linear war.

The specter of mass casualty biological weapons attacks — whether by nations or terrorists — is unrealistic. The United States should not overreact to the threat of biological weapons. Although the threat from biological weapons has not vanished, it is, in fact, at one of its lowest points since the Cold War’s end. Biological weapons are primarily a tool of assassination — largely for purposes of ensuring regime security in authoritarian states — and special forces operations. U.S. policymakers should strengthen diplomatic and intelligence community efforts to protect the American people from this enduring — but manageable — threat.

The History of Biological Weapons Use

During the Cold War, several nations developed biological weapons for potential military use.  Scholar W. Seth Carus identified 15 national biological weapons programs active from 1915 to the end of the Cold War. He points out that the number of national biological weapons programs fluctuated, with the majority lasting for only a short time.  The number of biological weapons programs during the Cold War fluctuated from between eight to five.

The development and possession of biological weapons is trending dramatically downward since the end of World War II. With the 1975 Biological Weapons Convention, signatories placed biological weapons use beyond the pale and the use of biological weapons has been stigmatized. After the Cold War, countries largely abandoned large-scale counterforce or countervalue biological weapons capabilities, and those that retained biological weapons programs focused on its utility for assassinations and sabotage operations in the immediate prelude to conflict. Although not a new capability, however, the potential use of biological weapons by special operations forces or intelligence operatives against fixed targets like naval bases, ports, and airbases was particularly attractive to some countries.

Despite the Biological Weapons Convention and international efforts to combat the biological weapons threat, concerns about biological weapons use remain. The United States currently assesses only one country (North Korea) possesses an offensive biological weapons program and three countries (China, Iran, Russia) are engaged in activities that raise concerns about their compliance to the Biological Weapons Convention.

Nations likely no longer see utility in developing or possessing biological weapons for use in large-scale, offensive military operations given the devastating capabilities of today’s advanced conventional weapons.

Even as a deterrent, biological weapons have little-to-no utility against an adversary contemplating the use of biological weapons. Historically, almost all nations possessing biological weapons saw it as a deterrent against adversarial use. Most nations renounced first-use of biological weapons, holding biological weapons only to retaliate in kind. The use of weaponized Yersinia pestis (the causative agent of plague) by Imperial Japan against China during World War II is a glaring exception. In that case, Japan used biological weapons against a numerically superior opponent incapable of retaliation. Other cases of biological weapons use during World War II included the small scale use by Polish resistance against German occupation and the Nakam revenge attack against German prisoners of war immediately after the war’s end.

Typically, biological weapons-related activities are observable when they reach larger-scale weaponization, dissemination testing, and military biological weapons training. The early stages of biological weapons development and production are much harder to uncover. Given the challenges involved in accurately detecting and identifying of biological weapons programs, it is no wonder that the track record of most intelligence agencies in assessing the existence of biological weapons programs is dismal. Western intelligence agencies failed to correctly identify and characterize the Soviet Union’s large biological weapons program, Iraq’s medium-size program before Desert Storm, and smaller programs such as those in Rhodesia, South Africa, and Chile.

Identifying or attributing the covert use of biological weapons to an actor is fraught with challenges and uncertainties. Any level of retaliation beyond diplomatic protests and expulsions needs to meet a very high bar. The seven-year Amerithrax investigation or the current controversies over COVID-19’s origins highlight the difficulties underlying attribution of a biological event. This likely incentivizes small-scale, covert biological weapons programs for some countries’ intelligence services or special forces.

The Role of Biological Weapons in the “Shadow War”

Do biological weapons have any role in the “Silent War” between great powers? They do, but that role is limited to assassination attempts and special operations forces. In that sense, things have not changed since the Cold War. Targets of these assassination plots typically were political opponents, dissidents, journalists or academics critical of a regime, defectors, and individuals deemed a security threat. The goal of covert biological weapons use in assassinations historically was not messaging, signaling, or as one author described it, “theatrical murder.” The goal is nonattributable assassination of key targets, typically to reinforce regime security. Messaging to deter potential opponents from speaking or acting against the regime is largely a second-order effect, with recent Russia use of Novichok agents being an exception.

Biological weapons use in special forces operations would concentrate on covert attacks against enemy leadership, military command and control infrastructure, deployment areas, military airfields, and naval ports during the prelude to conflict. Use in these scenarios is “subliminal,” to use a term popularized by David Kilcullen. This type of biological weapons use is not new. Fears of biological weapons sabotage attacks by the Soviet Union during the Cold War reach as far back as the 1957 National Intelligence Estimate on Soviet abilities to attack the continental United States.

Given realistic biological weapons threats focus largely on assassinations and special operations forces, embracing a deterrence by denial strategy against biological threats misses the mark. Under this strategy, a country would make major investments in public health in anticipation of a mass casualty attack on the American people. Although good reasons exist to increase funding for public health measures, the fear of biological weapons is not one of them. Doing so would assume an intent that is not currently evident and conflates intent with capability.

Lastly, it’s worth considering whether nations may secretly develop new or novel biological threat agents for use either in subliminal conflict (i.e., “gray war” or “hybrid war”) or to eliminate internal opponents (i.e., regime security). Detecting national biological weapons programs is an exceptionally difficult problem for intelligence agencies. Most biological weapons-related research and development activities are small-scale and being dual-use can be easily hidden within legitimate civilian biological research either in academic institutions or pharmaceutical industries.

Terrorism and Biological Weapons 

The threat of terrorists using biological agents exists but is very limited. The fear of nonstate actors using biological agents rose with Aum Shinrikyo’s 1995 failed efforts to spread botulinum and anthrax in Japan. Fears of bioterror reached its most recent crescendo with the 2001 anthrax letter mailings, coming as they did within weeks after the 9/11 attacks. The threat of further bioterror attacks, however, never materialized.

Despite the fact that terrorist biological weapons attacks have not materialized since the Amerithrax scare, some continue to argue that the supposed ease and lower cost of biological weapons development, production, and use along with the societal disruption of COVID-19 has incentivized bad actors to adopt biological weapons. These concerns have been echoed by others who assume that misuse is inevitable and following the COVID-19 example will result in mass casualties and crippling political, societal, and economic repercussions.

However, the bioterror threat seems to have diminished — not grown — since the 2001 Amerithrax letter mailings. The core al-Qaeda biological weapons efforts were first envisioned in the late 1990s and began in earnest shortly afterward. Yet the U.S. invasion of Afghanistan and the fall of the Taliban in late 2001 effectively disrupted al-Qaeda’s biological weapons work which largely centered on anthrax. Left without a suitable safe haven, al-Qaeda was never able to reconstitute its biological weapons efforts. The Taliban’s return to power in Afghanistan, however, may result in a reemergence of al-Qaeda and its biological weapons ambitions. Time will tell whether the Taliban now will grant safe haven to al-Qaeda that could be used for biological weapons work. What is undoubted is that the Taliban and al-Qaeda have a shared history and have continued to work closely together. Without a presence in Afghanistan, U.S. intelligence will have a more difficult time detecting any resurgent al-Qaeda biological weapons efforts.

The threat of a biological weapons effort by the Islamic State in Iraq never materialized, although the group did manage to produce and use chemical weapons agents until that program was effectively disrupted. Other terrorist groups’ interest in biological weapons has been rudimentary with a focus predominately on toxins such as ricin and botulinum. U.S. domestic extremists, self-radicalized individuals, and lone actors also have gravitated toward ricin, but no known casualties have resulted from the decades-long interest in ricin.

Some analysts, however, argue that the life science revolution and global proliferation of related scientific and technical capabilities has opened a Pandora’s Box of biothreats. The argument goes that the rapid revolution in genetic engineering — including synthetic biology — the DIY bio movement, and the advent of technologies like CRISPR (acronym for “clustered regularly interspaced short palindromic repeats”) makes their misuse likely. However, as noted in the 2018 National Academies of Science report, Biodefense in the Age of Synthetic Biology, the large-scale production and delivery of biological weapons agents is inherently difficult, with biological weapons use favoring small-scale, highly targeted attacks.


The threat of intentional, large-scale biological weapons dissemination likely is a thing of the past. Almost no nation, with the possible exception of North Korea, is intent on the theater-wide battlefield use of biological weapons. The threat today is that biological weapons will be used as a tool by intelligence services to assassinate or debilitate high-value targets, or by special forces to conduct small-scale, targeted attacks to sabotage facilities or deny their use by an adversary. Use of non-lethal biological weapons to degrade petroleum, oil, lubricants, and/or electronics almost certainly is more feasible today. In the context of great-power competition, biological weapons use also may be indirect (i.e., biological weapons use directed at a competitor’s allies or proxies/surrogates in a region). However, the recent chemical weapons use in assassinations and the use of chemical weapons in Syria — followed by a tepid international response — likely has incentivized the future use and development of biological weapons agents.

Biological weapons have a role in the “Shadow War” — which is far more insidious, far more difficult to detect, and far harder to defend against. It likely cannot be deterred using our current approaches and attribution is fraught with challenges, both technical and political.



Glenn Cross, Ph.D., is a former deputy national intelligence officer for Weapons of Mass Destruction responsible for biological weapons analysis. The views expressed here are solely those of the author in his private capacity and do not in any way represent the views, positions, or policies of the U.S. government including any of its constituent departments, agencies, or entities. The author wishes to thank an anonymous reviewer, W. Seth Carus, and Al Mauroni for their useful comments on this article.

Image: U.S. Air National Guard (Photo by Senior Airman Ryan Bishop)