IEDs are generally seen in heavy terrorist actions or in asymmetric unconventional warfare by insurgent guerrillas or commando forces in a theatre of operations. In the second Iraq War, IEDs were used extensively against US-led invasion forces and by the end of 2007 they had become responsible for approximately 63% of coalition deaths in Iraq. They are also used in Afghanistan by insurgent groups, and have caused over 66% of coalition casualties in the 2001–present Afghanistan War.
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. IEDs are extremely diverse in design and may contain many types of initiators, detonators, penetrators, and explosive loads.
Antipersonnel IEDs typically also contain fragmentation-generating objects such as nails, ball bearings or even small rocks to cause wounds at greater distances than blast pressure alone could. In the conflicts of the 21st century, anti-personnel improvised explosive devices (IED) have partially replaced conventional or military landmines as the source of injury to dismounted (pedestrian) soldiers and civilians. These injuries were recently reported in BMJ Open to be far worse with IEDs than with landmines resulting in multiple limb amputations and lower body mutilation. This combination of injuries has been given the name "Dismounted Complex Blast Injury" and is thought to be the worst survivable injury ever seen in war.