Improvised explosive devices (IED)

DEFINITION: Explosive weapons that are made of readily available materials and are concealed in some manner before detonation.

SIGNIFICANCE: Improvised explosive devices are the main weapons used against conventional military forces during low-intensity conflicts. Such devices, which are used both to intimidate and to injure intended recipients, enable terrorists to inflict casualties without having to expose themselves to retaliation. Given the increasing threat of terrorism around the world (persistent global threats and its geographic reach increased in 2024), law enforcement agencies must be familiar with the techniques used in the building and detonation of improvised explosive devices.

Improvised explosive devices (IEDs) are popular weapons among terrorists and insurgents. An IED consists of an explosive, a container to hold the different parts of the weapon, and a detonator. IEDs are effective and relatively easy to manufacture, requiring very little training to build. Persons who build IEDs may follow directions found in published manuals or on the Internet.

The use of IEDs was largely pioneered by T. E. Lawrence (known as Lawrence of Arabia), a British officer in the Middle East during World War I, though improvised explosive devices had been used earlier in other conflicts. Lawrence made effective use of mines, which he planted along railways to disrupt transportation during the Arab Revolt. IEDs have evolved since Lawrence’s time to include a wider array of explosives and less conventional additions to the composition of the device. Many terrorists and insurgents plant IEDs along the sides of well-traveled roads to cause maximum damage to vehicles and personnel. Often, an IED explosion signals the onslaught of an ambush by armed insurgents or more IEDs.

IEDs are also employed by more traditional criminal offenders, who use them to intimidate or for the express purpose of killing or wounding their targets. In such cases, the IEDs are generally mailed or delivered to the homes or businesses of the intended targets.

IEDs can be triggered in a few different ways. When detonation is achieved by remote control or by cell phone, the individual setting off the weapon must be in the vicinity of the device. Alternatively, a timing mechanism may be employed, or the device may be booby-trapped so that it is triggered by the intended victim. In a method often used by insurgents, IEDs can be strung together and set to explode when any one of the weapons in the string is detonated.

Very often, an IED explosion does not destroy all the device’s components. By examining all recovered remnants, forensic experts may be able to attribute the device to its source. Some IED makers leave “signatures” on their bombs that can help investigators link multiple bombings to the same suspect. In addition, investigators may use infrared spectroscopy to examine residues left by an explosion to determine the chemical composition of the explosive materials.

The type of triggering device used in an IED can provide investigators with a meaningful clue, particularly as to motive. If the bomb was booby-trapped, the intent was likely to kill the victim. In contrast, if the IED was triggered by a timer, it is possible that it was designed as a message to the recipient.

IEDs are discovered in a wide variety of ways. Many government agencies, including the Department of Homeland Security, have policies in place to handle improvised explosive devices. If civilians encounter something they suspect might be an IED, they should immediately contact local authorities for further investigation. Under no circumstances should a civilian attempt to interact with an IED.

Bibliography

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“IED Attack: Improvised Explosive Devices.” Department of Homeland Security, www.dhs.gov/xlibrary/assets/prep_ied_fact_sheet.pdf. Accessed 5 Mar. 2026.

“Improvised Explosive Devices (IEDs).” Department of Homeland Security, 19 Dec. 2022, www.dhs.gov/topic/explosives. Accessed 5 Mar. 2026.

Schubert, Hiltmar, and Andrey Kuznetsov, editors. Detection and Disposal of Improvised Explosives. Springer, 2006.

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