What is a Chemical Weapon?

The Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on Their Destruction, known as the Chemical Weapons Convention (CWC) defines chemical weapons in three parts:

1. All toxic chemicals (any chemical that can cause death/temporary incapacitation/permanent harm to humans or animals) and their precursors (chemicals involved in the production stages for toxic chemicals), except those used for:

  • Peaceful uses
  • Protection against toxic chemicals
  • Military purposes not related to the use of toxic chemicals as a method of warfare
  • Law enforcement, including domestic riot control purposes

2. Munitions and devices specially designed to release toxic chemicals (e.g mortars, artillery shells, missiles, bombs, mines or spray tanks that are designed and built with the intent to release toxic chemicals).

3. Any equipment specifically designed for use with such munitions or devices.

The toxic component of a chemical weapon is its chemical agent. These are commonly separated into five categories:

1. Choking agents – typically inhaled, causes a flow of liquid to enter the lungs, drowning the victim.

2. Blister agents – oily substance acts via inhalation and skin contact to cause large blisters and severe burns affecting the eyes, skin and breathing.

3. Blood agents – typically enter the body via inhalation and destroys the blood’s ability to use oxygen, causing the body to suffocate.

4. Nerve agents – typically act through absorption through the skin and lungs, blocking impulses of the nerve cells or synapses to cause seizures, loss of body control, paralysis of muscles including the heart.

5. Riot control agents – these agents are tear gas and pepper spray. Absorbed through lungs, skin and eyes. Constricts the airway, irritation to eyes, causes tears and coughing. Riot control agents are prohibited in warfare under the CWC, but are permitted for law enforcement purposes.


  • The Strasbourg Agreement in 1675 was the first international agreement limiting the use of chemical weapons. The Agreement only covered the limitation of poison bullets.
  • Earliest significant declaration on chemical weapons is The Hague Declaration in 1899, prohibiting the use of asphyxiating or deleterious gases. 26 nations in the 1899 conference took part. 
  • The Hague Declaration only focused on the use of chemical weapons. The first treaty to mention the manufacturing and importing, as well as the use of chemical weapons, was the Treaty of Versailles of 1919, but that only prohibited Germany from doing such actions:

Article 171: “The use of asphyxiating, poisonous or other gases and all analogous liquids, materials or devices being prohibited, their manufacture and importation are strictly forbidden in Germany. The same applies to materials specially intended for the manufacture, storage and use of the said products or devices.”

The Treaty of Versailles was the key treaty in bringing World War I to an end, involving the Allies and Associated Powers and Germany (a total of 28 States involved).

  • In 1925 there was the Geneva Protocol. It was the first truly global multilateral attempt to prohibit the use of chemical weapons. The Geneva Protocol was significant because it was signed by virtually the entire international community, whereas The Hague Declaration and the Versailles treaty had a limited number of signatories. Today there are 140 States Parties to the Geneva Protocol. It indicated to the entire international community that the use of these weapons should not be tolerated.

The Geneva Protocol prohibits the use in war of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices, and bacteriological methods of warfare.

  • The Hague Declaration of 1899 and the Geneva Protocol of 1925 only focused on the use of chemical weapons. It was only in 1919 that The Treaty of Versailles mentioned the manufacturing and importing of chemical weapons, but only towards Germany. The Chemical Weapons Convention (CWC) in 1997 was innovative in that it was the first treaty that prohibited the development, production and stockpiling of chemical weapons in addition to use of chemical weapons. It was near universally embraced, States Parties cover about 98% of the global population and landmass. As of June 2017, there are 192 States Parties to the Convention. 1 State has signed but not ratified (Israel). 3 States have neither signed nor ratified: Egypt, DPR Korea ("North Korea"), South Sudan.

The CWC’s relative easiness to secure near universal ratification was brought out of events prior to 1997. It led to State actors (and non-state actors such as NGOs and advocacy groups) supporting the Convention.

Use of Chemical Weapons

Chemical Weapons were used by Iraq on the Iranians in the 1980s. According to the US Central Intelligence Agency, Iraq fired or dropped over 100,000 chemical munitions against Iranian forces.

Iraq’s use of chemical weapons brings to light one of the problems with international law in general - there are limited enforcement measures. Iraq is a member of the 1925 Geneva Protocol, yet that did not prevent them from using chemical weapons.

Saddam Hussein used chemical weapons against the Kurdish people in Halabja, Iraq in 1988. Up to 5,000 people died on the day and up to 12,000 have lost their lives since.

The first large scale use of chemical weapons was by Germany in World War I between 1915 and 1918. 1.3 million casualties and 90,000 fatalities from chemical weapons occurred in Belgium.

Impact of the CWC and Military Advances

  • The CWC is unique in that has detailed verification and enforcement measures on chemical weapons, something that the Geneva Protocol lacked. This leads to the likelihood of state adherence. The CWC established the monitoring body Organisation for the Prohibition of Chemical Weapons (OPCW) in The Hague, the Netherlands.
  • Combining the detailed verification and enforcement measures together with the amount of States parties to the CWC, it creates a negative image of chemical weapons. States are reluctant to use them. It makes more sense to use conventional weapons instead.
  • The strategic and tactical value of chemical weapons is limited. Conventional weaponry has developed to such a level that the reason for using chemical weapons to gain an advantage is weakened. Also, military defence are well equipped to deal with chemical weapons. Soldiers have gear to wear that can protect them from it and fight.
  • The civilian population may be vulnerable to chemical weapons, but to kill/cause great suffering to civilians in warfare violates international humanitarian law (Fourth Geneva Convention), constituting its use a war crime: 

Convention (IV) relative to the Protection of Civilian Persons in Time of War. Geneva, 12 August 1949.

Art. 147. Grave breaches to which the preceding Article relates shall be those involving any of the following acts, if committed against persons or property protected by the present Convention: wilful killing, torture or inhuman treatment, including biological experiments, wilfully causing great suffering or serious injury to body or health, unlawful deportation or transfer or unlawful confinement of a protected person, compelling a protected person to serve in the forces of a hostile Power, or wilfully depriving a protected person of the rights of fair and regular trial prescribed in the present Convention, taking of hostages and extensive destruction and appropriation of property, not justified by military necessity and carried out unlawfully and wantonly.

On the Destruction of Chemical Weapons

  • The CWC expresses that States parties must provide a plan for the destruction of their chemical weapons, and gives deadlines for the destruction of them.
  • The deadlines begin from the date the CWC enters into force. The CWC entered into force on 29 April 1997. Deadlines are split into three categories and four phrases.
  • The deadline given by the CWC to destroy all chemical weapon stockpiles was April 2012 at the latest. 
  • Some countries who had chemical weapons prior the entry into force of the treaty have found it difficult to destroy all stockpiles in time.
  • The latest annual report by the Organisation for the Prohibition for Chemical Weapons (OPCW) published in November 2016 expresses that there are still five States Parties with declared chemical weapons: Iraq, Libya, the Russian Federation, the Syrian Arab Republic and the United States of America.

The deadlines have passed, why haven't these states destroyed all their chemical weapons?

This is mainly due to the environmental and safety hazards involved in the destruction of chemical weapons. Destroying large amounts of chemical weapons in suitable facilities complying with thorough regulations take time. Also and in particular to Iraq, Libya and the Syrian Arab Republic, due to ongoing security concerns, the States have found it difficult to destroy their stockpiles.

How are Chemical Weapons Destroyed?

  • In non-descript buildings. Facilities would be in remote locations away from residential areas, communities don’t want these destruction facilities to be close to them (same with nuclear waste).
  • The main method of destroying chemical weapons is through incineration. Destruction facilities are equipped with high heat incinerators. Another method used is hydrolysis, where the chemical agents are mixed with water to weaken their potency.


Other references:

Ryan Scoville, Professor of Law

Chemical Weapons Convention

Organisation for the Prohibition of Chemical Weapons

Types of Chemical Weapons Fact Sheet