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Chemical and Biological Weapons
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The history, science, and international law surrounding chemical and biological weapons, from World War I trenches to modern arms control challenges.
Chemical weapons entered modern warfare on April 22, 1915, when German forces released 168 tons of chlorine gas at Ypres, Belgium. The gas cloud drifted across Allied trenches, causing panic and thousands of casualties. Both sides quickly escalated, deploying phosgene, mustard gas, and other agents. By the war's end, chemical weapons had caused roughly 1.3 million casualties, including 90,000 deaths. The horror of gas warfare led to the 1925 Geneva Protocol, which prohibited the use (but not production or stockpiling) of chemical and biological weapons.
Biological weapons have a longer but less extensive combat history. Japan's Unit 731 conducted grotesque biological experiments and attacks in China during World War II. During the Cold War, both the US and Soviet Union maintained massive biological weapons programs. The US unilaterally renounced its program in 1969, but the Soviet Union secretly continued its Biopreparat program, employing tens of thousands of scientists to weaponize anthrax, smallpox, and plague, a violation of the 1972 Biological Weapons Convention.
Two treaties form the backbone of the chemical and biological weapons prohibition. The Biological Weapons Convention (BWC) of 1972 bans the development, production, and stockpiling of biological agents for hostile purposes. However, the BWC has no verification mechanism, making compliance impossible to confirm. Efforts to add verification provisions have been blocked, primarily by the United States, which argued the measures would compromise commercial biotechnology secrets.
The Chemical Weapons Convention (CWC) of 1993 is far more robust. It bans the development, production, stockpiling, and use of chemical weapons and established the Organisation for the Prohibition of Chemical Weapons (OPCW) to verify compliance through inspections. Over 98 percent of the world's declared chemical weapons stockpiles have been destroyed under OPCW supervision. The OPCW received the Nobel Peace Prize in 2013 for its work, particularly its emergency mission to destroy Syria's declared chemical weapons stockpile.
New challenges are testing the chemical and biological weapons taboo. The 2018 Novichok poisoning of former Russian spy Sergei Skripal in the UK demonstrated that states are willing to use nerve agents for targeted assassination on foreign soil. The rapid pace of biotechnology advancement, including gene editing tools like CRISPR, raises concerns about the creation of novel biological agents that existing treaties were not designed to address.
Synthetic biology could theoretically enable the creation of pathogens that target specific genetic traits or resist all known treatments. While such capabilities remain largely theoretical, the dual-use nature of biotechnology research means that the same tools used for legitimate medical research could be repurposed for weapons development. Strengthening the BWC verification regime and expanding biosecurity norms are among the most pressing arms control challenges of the coming decades.
Both categories are banned by treaty, but the regimes are not equally strong. Compare them directly:
| Feature | Chemical Weapons Convention (CWC, 1993/entered force 1997) | Biological Weapons Convention (BWC, 1972/entered force 1975) |
|---|---|---|
| Implementing body | OPCW (won the 2013 Nobel Peace Prize) | None; no dedicated verification organisation |
| Verification | Routine and challenge inspections of declared industry | No inspection mechanism; a 2001 verification protocol collapsed |
| Destruction record | Over 99% of declared stockpiles verifiably destroyed | Not applicable; no declared-stockpile system |
The gap is verification. Chemical agents require bulk industrial production that inspectors can watch; biological agents can be brewed in small dual-use labs indistinguishable from legitimate vaccine or pharmaceutical work, so states never agreed to intrusive checks. Real-world tests of the CWC regime, Syria's 2013 sarin attack in Ghouta (which prompted its accession and partial disarmament) and the 2017-2018 Novichok cases, showed the OPCW could attribute and investigate even as violations occurred. The BWC, lacking teeth, relies mostly on norms and confidence-building. Same goal, very different enforcement.
