U.S., Soviet Union, and dozens of nations open treaty banning biological weapons

Story: 1972 C.E.  |  Last updated: April 10, 1972

On April 10, 1972 C.E., representatives gathered simultaneously in London, Moscow, and Washington, D.C., to sign one of the most consequential disarmament agreements in history. For the first time, nations were committing — in writing, and in international law — to never develop, produce, or stockpile an entire category of weapons capable of killing millions. The Biological Weapons Convention was born.

What the treaty established

• Biological weapons ban: The BWC prohibited the development, production, acquisition, transfer, stockpiling, and use of biological and toxin weapons — the first multilateral treaty to ban a full class of weapons of mass destruction.
• Disarmament treaty scope: The convention applied not just to state militaries but to any actor, including non-state groups, closing off the legal space for biological weapons programs across the board.
• General-purpose criterion: Rather than listing specific banned agents, the treaty outlawed any biological material weaponized for hostile purposes — a flexible standard designed to cover agents not yet discovered or engineered.

A long road to the signing table

Biological warfare is not new. Historians trace its deliberate use back at least to 1346 C.E., when Mongol forces catapulted plague-infected bodies into the besieged city of Caffa on the Black Sea — an act that may have helped spread the Black Death into Europe. Six centuries later, the international community was still struggling to put meaningful limits on the practice.

The 1925 Geneva Protocol was the first major international step. It banned the use of biological and chemical weapons in war, but left development and stockpiling untouched. In practice, it functioned as a no-first-use agreement at best. Multiple nations, including the United States and the Soviet Union, continued building offensive biological weapons programs well into the Cold War era.

The United States ran an active biological weapons program from 1943 until 1969 C.E., when President Nixon unilaterally terminated it — unconditionally, without requiring reciprocal action from any other nation. That decision, unusual in the history of arms control, changed the diplomatic math. It gave the U.S. credibility to push for a binding international ban and helped unlock negotiations that had been deadlocked for years.

A 1968 British proposal had suggested separating biological and chemical weapons in treaty negotiations — dealing with the more tractable biological weapons first. The U.S. endorsement of that approach, following Nixon’s program termination, gave it momentum. By March 1971 C.E., the Soviet Union reversed its opposition and tabled its own draft convention. In August 1971 C.E., the U.S. and Soviet Union submitted identical but separate draft texts — a rare moment of Cold War convergence. Negotiations concluded, and the treaty was opened for signature the following April.

The biological weapons ban enters history

The Biological Weapons Convention entered into force on March 26, 1975 C.E., after ratification by 22 states, including the three depositary governments: the United States, the United Kingdom, and the Soviet Union. As of May 2025 C.E., 189 states are party to the treaty.

That near-universal membership reflects something more than legal compliance. According to the treaty’s preamble, the use of biological weapons would be “repugnant to the conscience of mankind.” That language — moral rather than merely technical — was deliberate. Treaty architects wanted to establish not just a rule but a norm.

It worked, at least in part. Today, no state openly declares it possesses or seeks biological weapons. No government publicly asserts that their use in war is legitimate. Biodefense expert Daniel Gerstein has called the BWC “the most important arms control treaty of the twenty-first century” — a striking claim, given the competition.

What this made possible: lasting impact

The BWC established the legal and moral architecture that subsequent arms control efforts built on. The 1993 Chemical Weapons Convention borrowed directly from the BWC’s general-purpose criterion — the flexible, intent-based standard that bans hostile uses of any agent regardless of whether it exists yet. That design principle has proved durable across decades of technological change.

The treaty also helped create the conditions for global cooperation on infectious disease response. When nations agree that biological agents must not be weaponized, they create a shared vocabulary and a shared stake in monitoring outbreaks. The norm against biological weapons reinforced the legitimacy of international health surveillance — infrastructure that would become critical during the COVID-19 pandemic and future outbreaks.

Perhaps most importantly, the BWC demonstrated that Cold War adversaries could agree to dismantle a weapons category entirely. That precedent — not just arms limitation, but prohibition — remained a touchstone for disarmament advocates and negotiators for decades.

Blindspots and limits

The BWC’s most significant weakness is the one it has carried since birth: there is no formal verification mechanism. Unlike the Chemical Weapons Convention, which created the Organisation for the Prohibition of Chemical Weapons with inspection authority, the BWC has no independent body empowered to monitor compliance or investigate suspected violations. Negotiations over a verification protocol collapsed in 2001 C.E. and have not been revived.

That gap has had real consequences. The Soviet Union ran one of the largest covert offensive biological weapons programs in history — code-named Biopreparat — well after ratifying the BWC, continuing until at least 1992 C.E. Ba’athist Iraq also violated the convention. The treaty’s complaint mechanism, outlined in Article VI, has been invoked only once — by Russia in 2022 C.E., in connection with a widely debunked conspiracy theory about Ukraine. The convention has also faced sustained criticism for being underfunded and institutionally fragile, with scholars calling for modernization to address advances in synthetic biology, CRISPR, and gain-of-function research.

None of that erases what the treaty accomplished. But it is a reminder that a norm, however powerful, is not the same as enforcement.

Read more

For more on this story, see: Biological Weapons Convention — Wikipedia

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