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IED Attack: What It Is

Examples of Terrorist IED Attacks

Oklahoma City Bombing
On the morning of April 19, 1995, a truck bomb exploded in front of the Alfred P. Murrah Federal Building in Oklahoma City, Oklahoma. The bomb was improvised from ammonium nitrate fertilizer and nitromethane, which were put into the back of the truck and left to explode. It was the worst terrorist attack on U.S. soil up to that time, killing 169 people. Timothy McVeigh was convicted and executed for the crime; his accomplice, Terry Nichols, is serving a life sentence in federal prison.

Madrid Train Attacks
Ten explosions rocked through four commuter trains during rush hour on March 11, 2004, in Madrid, Spain. The bombs had been made from bags stuffed with explosives, allegedly the explosive known as Goma-2 ECO, and metal fragments; cell phones with timers were used to initiate the explosive devices. The attack, which was carried out by violent Islamist extremists, killed 191 people, and injured more than 1,800.

July 2005 London Bombings
Fifty-two people were killed and hundreds more injured in a series of coordinated attacks on the London transportation system on the morning of July 7, 2005. The attacks were carried out by four suicide bombers. Authorities had difficulty identifying the explosive used in the IEDs; they believe it was TATP on the basis of finding TATP in the London apartment of the biochemist arrested in Cairo in association with these bombings.

Olympic Park Bombing
In the midst of the 1996 Olympics, an IED composed of "pipe bombs" concealed in a backpack exploded in the Centennial Olympic Park in Atlanta, Georgia, where the games were being hosted. The bomb contained nails to increase its lethality. Two people died and many were injured. Eric Rudolph pleaded guilty in 2005.

An improvised explosive device (IED) attack is the use of a "homemade" bomb and/or destructive device to destroy, incapacitate, harass, or distract. IEDs are used by criminals, vandals, terrorists, suicide bombers, and insurgents. Because they are improvised, IEDs can come in many forms, ranging from a small pipe bomb to a sophisticated device capable of causing massive damage and loss of life. IEDs can be carried or delivered in a vehicle; carried, placed, or thrown by a person; delivered in a package; or concealed on the roadside. The term IED came into common usage during the Iraq War that began in 2003.

Elements of an IED

IEDs consist of a variety of components that include an initiator, switch, main charge, power source, and a container. IEDs may also include additional materials such as nails, glass, or metal fragments designed to increase the amount of shrapnel propelled by the explosion. An IED can be initiated by a variety of methods depending on the intended target.

Materials Used as Explosives in IEDs

Many commonly available materials, such as fertilizer, gunpowder, and hydrogen peroxide, can be used as explosive materials in IEDs (see Table 1). Explosives must contain a fuel and an oxidizer, which provides the oxygen needed to sustain the reaction. Concern about explosives created from liquid components and transported in a stable form and mixed at the attack site is the reason behind the Department's restriction on liquids that passengers can carry on commercial aircraft.

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