Chemical and biological weapons

The use of poisons and poisoned weapons as a method of warfare has been practised since ancient times, ranging from poisoned arrows and spears, to poisoning wells and food supplies, to the dispersion of toxic gases and the release of disease-causing agents. The first recorded use of poisonous gases as a method of warfare dates back at least as far as 431–402 bce when the Spartans burnt mixtures of sulphur and pitch when besieging Athenian cities.¹ A similar mixture of toxic chemicals (subsequently called ‘Greek Fire’) was used by the Byzantine navy in the seventh century.² Other early examples of chemical warfare include the dispersion smoke containing toxic compounds of arsenic.³ Likewise, biological warfare since the Middle Ages has included the poisoning of food and wells, and the deliberate spread of diseases, including by catapulting diseased bodies and excrement over city walls, the use of plague against Swedish troops in 1710 and the use of smallpox against American Indians in 1763.⁴