An improvised explosive device (IED) is a bomb constructed and deployed in ways other than in conventional military action. It may be constructed of conventional military explosives, such as an artillery shell, attached to a detonating mechanism. IEDs are commonly used as roadside bombs, or homemade bombs.
The term "IED" was coined by the British Army during the Northern Ireland conflict to refer to booby traps made by the IRA, and entered common use in the U.S. during the Iraq War.
IEDs are generally utilized in terrorist operations or in asymmetric unconventional warfare by insurgent guerrillas or commando forces in a theatre of operations. In the Iraq War (2003–2011), insurgents used IEDs extensively against U.S.-led forces and, by the end of 2007, IEDs were responsible for approximately 63% of coalition deaths in Iraq. They were also used in Afghanistan by insurgent groups, and caused over 66% of coalition casualties in the 2001–2021 Afghanistan War.
IEDs were also used frequently by the Liberation Tigers of Tamil Eelam (LTTE) in Sri Lanka during the Sri Lankan Civil War, and by Ambazonian separatists in the ongoing Anglophone Crisis.
An IED is a bomb fabricated in an improvised manner incorporating destructive, lethal, noxious, pyrotechnic, or incendiary chemicals and designed to destroy or incapacitate personnel or vehicles. In some cases, IEDs are used to distract, disrupt, or delay an opposing force, facilitating another type of attack. IEDs may incorporate military or commercially sourced explosives, and often combine both types, or they may otherwise be made with homemade explosives (HME). An HME lab refers to a Homemade Explosive Lab, or the physical location where the devices are crafted.
An IED has five components: a switch (activator), an initiator (fuse), container (body), charge (explosive), and a power source (battery). An IED designed for use against armoured targets such as personnel carriers or tanks will be designed for armour penetration, by using a shaped charge that creates an explosively formed penetrator.