Detonating the air: The legality of the use of thermobaric weapons under international humanitarian law

Abstract Thermobaric weapons cause damage and harm through overpressure and thermal effects, but secondary harm may also occur due to fragmentation, the consumption and depletion of ambient oxygen, and the release of toxic gases and smoke. Several international instruments prohibit or regulate weapons that generate asphyxiating or toxic gases, poison or poisoned weapons, chemical weapons, and weapons primarily designed to be incendiary. Thermobaric weapons are, however, primarily designed for blast and are not specifically covered by, or excluded from, the application of these instruments. The general customary law principles of international humanitarian law that determine the legality of the use of all weapons, including thermobaric weapons, prohibit causing superfluous injury and unnecessary suffering, and the use of indiscriminate weapons. Thermobaric weapons cause severe suffering but will not be rendered unlawful merely because of this effect. These weapons are also not automatically and inherently indiscriminate when used in their normal or designed circumstances. The use of thermobaric weapons, when directed at a military objective, while considering all feasible precautions to protect civilians and civilian objects and the principle of proportionality, will, as a result, be lawful in most circumstances. However, the use of thermobaric weapons should, in a similar manner to heavy explosive weapons, be avoided in urban or populated areas.