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An examination of the precursor chemicals used in the manufacture of explosive compositions found within Improvised Explosive Devices (IEDs)

Chapter 8: Case Studies and Annexes


The activities of the Provisional Irish Republican Army that sought to end British rule of Northern Ireland started in 1969 with the beginning of attacks on police, British troops and law enforcement at large. The attacks carried out over the years using IEDs killed over 1,800 people, including over 650 civilians. The different brigades of PIRA gained expertise in building IEDs and, as their knowledge of chemical materials and craftsmanship grew, the attacks became more precise and IEDs more stable, thus reducing civilian casualties, though that was not a specific goal of the armed group.

The UK successfully banned the use of AN-based fertilizers with a nitrogen content of more than 27.5% by mass in late 1972 [20]. This legislation was put in place to counter the large devices being used by PIRA and the Official IRA (OIRA) [21], following restrictions imposed on commercial explosives. However, the requirement for fertilizer endured in an agricultural

economy and the move to calcium ammonium nitrate (CAN) was sanctioned. Royal Armament Research and Development Establishment (RARDE) tests confirmed that the diluent, when added to 79% AN, was incapable of being detonated even with a booster [22]. However, PIRA chemists soon developed a countermeasure. Mixing CAN in hot water dissolved AN, thereby separating it from the diluent and producing almost pure AN in the process. Detonations up to 0.92 TNT equivalence were achieved with the product and certain fuels. As such, AN distilled from CAN continued to be used but its introduction made the manufacturing process time-consuming, thereby reducing the number of large-scale attacks.

PIRA continued working with CAN and in early 1991 a marked step change occurred. Prill grinders and crushers were used to powder CAN into a detonable state when combined with additives such as sugar and aluminium. The UK mainland became the target of interest and five major bombings took place using CAN between 1991 and 1996. The combined weight of HME used in these attacks was close to 6000 kg, causing well over GBP £1.45 billion damage.

The IRA bombing of the Arndale Centre, Manchester, 1996. By mrrobertwade (CC BY-NC-SA 2.0).

As for any counter terrorism measure, there will always be a counter to any legislative approach. This must be anticipated through predictive threat analysis and a deep analysis of the social and structural drivers within the targeted group. As the British response to PIRA exemplifies, states with strong institutions can rapidly implement legislation to protect security freedoms. States without robust institutions find it difficult to maintain the physical security of military and commercial stockpiles. If the supply chain allows it, the use of military and commercial explosives is the preferred choice of perpetrators given their improved performance and reliability over HME – examples Iraq, Syria, Libya, Yemen, Somalia.

The long conflict in Afghanistan has seen more than 157,000 people die and the use of improvised explosive devices at growing rates. [23] IEDs have been the leading cause of conflict-related civilian death in Afghanistan every year since 2001, excluding 2014 and 2016 when a higher number of casualties derived from ground engagement and fighting between Afghan forces and the Taliban, also corresponding to the time in which the Taliban military activity has been strongest. The Taliban are considered responsible for the majority of IED attacks in Afghanistan after 2001. Despite the Taliban public condemnation of attacks harming civilians, said attacks became widely spread after 2009. 80% of all IED attacks on US troops were carried out by ammonium nitrate or other precursor based IEDs. The precursor used in IEDs’ construction were smuggled from Pakistan where large industrial production is in place, into Afghanistan where they arrived in the hands of armed non-state groups. [24]

Weapons cache containing more than 100 lbs. of homemade explosives, pressure plates and bomb making material. Ghazni province, Afghanistan, 2012. Image: Department of Defence (CC BY-NC 2.0).

Pakistan in the early 2000’s had a large production of fertilizer containing ammonium nitrate in the country, production necessary for the country’s large agricultural sector, representing the main livelihood strategy for the majority of rural communities, as well as important for neighbouring Afghanistan’s agriculture, the national economy’s most developed sector. As ammonium nitrate was vastly used by the Taliban in building IEDs, the Afghan government reacted by issuing a ban in 2010 to all ammonium nitrate-based fertilizers in the country. The ban has increased the illegal smuggling of ammonium nitrate- based fertilizers across the border from Pakistan’s Punjab region to Afghanistan. The substance is taken across the border in trucks and it is often hidden into laundry detergent bags, and then collected by the Taliban, which remain the main perpetrator of IED attacks in the country as well as the main users of ammonium nitrate-based fertilizers in building IEDs.

The routes taken by smugglers varies from the more impervious ones used by drug traffickers, to border crossing. The lack of adequate law enforcement and border security has helped create a strong black market which guarantees easy access to the product by the Taliban.

The blanket ban of all ammonium nitrate-based fertilizers in Afghanistan has not only been a difficult policy to protect the civilian population from Taliban’s IED attacks, but it has also harmed the struggling agricultural sector of the country, pushing more farmers to return to opium production which is more profitable than other crops, especially when chemical fertilizers’ prices rise.

Since 2000, the accidental explosions that have involved ammonium nitrate, either due to industrial stockpiling, confiscation from the authorities or dumping of large amounts of ammonium nitrate sums to more than 13. These incidents have caused deaths and injuries among both the civilian population and the armed forces and security personnel. The most recent tragedy involving ammonium nitrate is the large explosion that took place on August 4th 2020 in the commercial port of Beirut, Lebanon. The large quantity of ammonium nitrate formerly confiscated by the Lebanese authorities and improperly stored in the port killed over 200 people and injured more than 2,500. The incident is the largest ammonium nitrate explosion ever recorded with 2750 tons. The large quantity of ammonium nitrate was stored in Beirut’s port after being confiscated in 2013 from cargo ship M.V. Rhosus.

Aftermath of the explosion in the port of Beirut, August 2020. By EU Civil Protection and Humanitarian Aid (CC BY-NC-ND 2.0).

The event in Beirut shed light on the importance of shared regulations in the commercialization, accumulation and safe stockpiling of ammonium nitrate and other dangerous precursor chemicals. Safety regulations vary from country to country, leaving less equipped states at risk due to the mismanagement of precursor chemicals and explosive substances at large. The United Nations Economic Commission for Europe’s Industrial Accidents Convention sets guidelines and policy advice for countries to react to the incidents caused by ammonium nitrate and other explosive materials.

The Convention primarily focuses on measures to be taken when storing and handling explosive substances, including ammonium nitrate. Lebanon is not among the ratifiers nor the signatories of the convention.

In Europe, stockpiles’ regulations are under the Seveso 3 directive (Directive 2012/18/EU) that strengthened laws in the aftermath of the explosion that took place at the AZF plant in Toulouse in France in 2001 and killed 31 people. The EU regulation aims to differentiate the security measures that have to be in place depending on the amount and the type of dangerous substance present. The US regulation on the accumulation of Ammonium Nitrate is less precise and only includes that where more than 2500 tonnes of ammonium nitrate are stored, the building needs to have an automatic fire extinguisher system in place. The large explosion that took place in Beirut has encouraged several states to review national policy on stockpiling of dangerous chemicals, in particular in countries where large deposits of these chemicals are present, such as the UK, Australia, Iraq and India.

The Islamic State created a strong and efficient network for the procurement of precursor chemicals, IED components and other potentially destructive materials. The elaborate network was based on passing these materials through several middlemen in order to cover the connection between the manufacturer and IS as the then user of such materials. The efficiency of the system appears clear when considering the large amounts of chemical materials that IS have received over the years from distant manufacturers without being traced, a situation drastically different from that of the Taliban in Afghanistan, who were most often receiving supplies of chemical materials from factories and producers in neighbouring Pakistan. The different steps within the procurement network that guaranteed the passage of precursor chemicals from one person to the other capitalizes on the economic difficulties that wars bring and a high level of individualism that characterizes life in failed or fragile states.

The procurement network often started in China (where most of the precursor chemicals used by
the Islamic State are produced) and ended in Iraq where the Islamic State’s production sites are located. A report by Conflict Armament Research revealed that over 50 companies and small businesses across more than 20 countries worldwide were to different degrees involved in the procurement network used by the Islamic State. The network was discovered due to the recurring inconsistency between the type of business that carried out the order and then sold it, and the need for precursor chemicals for the business itself. Among the orders that were traced, the typical route for the precursor chemicals and the other materials appeared to be through Turkey where they were passed between different hands and then smuggled into Syria and then onwards to Islamic State’s production sites in Iraq. Among the precursor chemicals used by the Islamic State to build HME and IEDs is leafing aluminium paste, which was found in six of the production sites used by the Islamic State to produce explosive devices across Iraq.

Inside of a rock bomb IED, found in Abyan, Yemen, March 2021.


It is recommended that Member States consider:
A study to examine the feasibility of a global chemical precursor strategy, which restricts, substitutes and standardizes regulatory thresholds to minimize their use in IED manufacture;

Noting that such a strategy would, over time, place Member States ahead of perpetrator capabilities and future intentions with respect to IED manufacture; the strategy should consider best practice approaches from existing regional / national strategies; the strategy should not be bound to the physical chemicals themselves but also to the manner in which their usefulness is publicised; focus should be applied initially to those chemical precursors deemed critical to the effective performance of the IED (such as detonator compositions).

And that: analysis of regional supply chains is required to identify the most common precursor materials available and to predict future threats; research programmes are necessary to identify viable chemical substitutes in the marketplace; a Humanitarian Mine Action (HMA) approach does not embrace the exploitation of IEDs. This hinders identification of trends in IED design and chemical precursor use and should be reviewed; there is no internationally recognised or standardised system from which to collect and share data; the Global IED Task Force and UNIDIR C-IED capability Maturity Model are available to Member States to further inform their understanding of chemical precursors and associated capacity building measures.


As a safety and security precaution, this paper will not reference the detailed techniques nor open-source reference materials that can be used to produce a viable home-made explosive (HME). HME mixtures can be highly unstable and be easily and inadvertently initiated due to heat, friction, static electricity or shock impact.


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