Many analysts consider chemical and biological weapons to be of limited military utility, in part because countermeasures exist to keep down battlefield casualties. Chemical weapons can produce high numbers of casualties when used against an unprotected civilian population, however. For example, Iraqi chemical attacks against the city of Halabja, a northern Iraqi Kurdish village held by Iran during the Iran-Iraq war, killed between 3,000 and 5,000 people. But history suggests killing civilians on this scale does not win wars between states.
What chemical and biological weapons can do is capture the worlds attention and create fear among possible victims. Saddam’s mere threat to use chemical weapons during the 1991 Gulf War caused thousands of citizens to evacuate Tel Aviv and Jerusalem, despite strong doubts that Iraq’s extended-range, reduced-payload Scuds could be used effectively to disseminate a chemical agent. With this capacity to fascinate and frighten, poisons may be ideally suited for terrorists, for whom creating fear in the target population is more important than creating casualties per se. To date, however, terrorists have used chemical and biological weapons rarely, and only to injure or kill small numbers of people. What constraints have held terrorists back? And are those constraints eroding?