How IEDs Work

An Iraqi police commando walks past the aftermath of a vehicle-borne IED attack in Kirkuk, Iraq. The war in Iraq has seen a massive uptick in the number of deadly IED bombings occurring. See more explosives pictures.
Marwan Ibrahim/AFP/­Getty Images

­A neighborhood in Iraq reverberates with a deafening explosion. A military convoy has been hit by a roadside bomb. The explosion has left a crater in its wake, ripped apart vehicles and injured the soldiers riding within them. In a nearby marketplace, a suicide bomber blows himself up, maiming and killing scores of nearby civilians. These violent scenes have played out repeatedly in Iraq and Afghanistan since combat operations began there in the early 21st century.

It wasn't always this way. In the beginning of the Iraq war, U.S. soldiers were injured mainly from gunfire, mortars and grenades. The injuries are wrought now by a different source. The preferred weapon of insurgents and terrorists has become an improvised explosive device, or IED. You might call it a homemade bomb or a booby trap. Whatever you call it, an IED is relatively simple to make, easily hidden and very destructive.

­Soldiers, civilians, as well as paramilitary and terrorist groups, have been building and detonating homemade bombs for years.

  • During the Vietnam War, the Viet Cong hid IEDs in soda cans because they observed that U.S. soldiers liked to kick empty cans while marching along the roads [source:].
  • The Irish Republican Army used them in the 1960s and 1970s during its struggles with the British in Northern Ireland.
  • In 1996, Eric Rudolph made a pipe bomb (IED) and set if off in Atlanta's Centennial Olympic Park during the Summer Olympics. One person died and more than 100 people were injured in the attack.

­You could fill volumes with all the IED attacks that have occurred within the last d­ecade. That's because IEDs can be an effective strategy when facing a superior or more technological military force. Guerilla fighters, rebels and terrorists employ the weapons mainly to harass the military and to terrorize civilians and governments. Their use shows no signs of abating.

In fact, roadside bombs, which are typically IEDs, have reigned as the No. 1 killer of U.S. troops in Iraq, although the number of IED casualties dropped substantially in August 2008 [source: McMichael]. In Afghanistan, however, IED attacks a­re up 50 percent in 2008 [source: NPR]. No wonder the U.S. military is actively researching countermeasures.

This article will explore the destructive world of IEDs -- how they're made and detonated, why they're so prevalent, how they injure people and how to protect people from them.

Up next: a look inside the deadly device.

Anatomy of an IED

A cordless phone is a popular remote trigger for an IED since it may allow a signal to be transmitted up to a mile.
A cordless phone is a popular remote trigger for an IED since it may allow a signal to be transmitted up to a mile.
Ed Darack/­Getty Images

Before we pick apart an IED, a refresher on more conventional bombs might be handy.

  • Landmines are planted within a designated area (a minefield) and are intended to bring down entering soldiers or vehicles.
  • Soldiers throw hand grenades over a short range to clear an area of enemy personnel.
  • Rocket-propelled grenades, or just RPGs, are launched over a larger range and can rid a target area of enemy personnel or destroy enemy vehicles.
  • Bombs are dropped from planes, are self-contained and controlled to devastate anything within a specific area.

Such bombs are commercially made. Armies purchase these weapons from defense contractors for military and training operations, although other individuals can obtain them through the thriving black market for weapons.

­In contrast, IEDs are homemade with five basic parts:

  1. A power supply, often provided by car batteries or alkaline flashlight batteries
  2. A trigger, switch or some other direct or indirect means of setting the device off, such as a radio signal, trip wire, timer or firing button that someone presses. A common form of remote trigger is a cell phone, cordless phone, radio or garage door opener activated by someone who is watching [source:].
  3. A detonator, a small explosive charge that sets off the main charge. Detonators are usually electrical, like those used for explosions in construction.
  4. A main charge, the primary explosive that's the big guns behind the blast. Unexploded landmines fit the bill.
  5. A container to hold everything together. The container may be designed to force the blast in a specific direction.

Additional components packed in the device may include projectiles for shrapnel, such as ball bearings, nails and stones, as well as hazardous, toxic or fire-starting chemicals. IEDs may also be used as the explosive part of a biological or radioactive dirty bomb.

Let's look at how these parts work together:

  1. The power source supplies electricity to the trigger or switch and to the detonator.
  2. The trigger activates the detonator and initiates the explosion sequence. The trigger may sense the target, be activated by the target, be a timed trigger or be operated remotely.
  3. The detonator explodes, thereby providing energy for the main explosive.
  4. The main charge explodes, producing a high-pressure shock wave or blast wave, and may propel shrapnel, toxic chemicals or fire-starting chemicals.

Here's the distressing part: IEDs are relatively simple to make with a little research, time and training. After all, how hard is it to get batteries, cell phones and radios? Detonators and explosives such as C-4, Semtex and dynamite can be found at construction sites and oil rigs. They also may be stolen, purchased legally or cooked up at home or in a makeshift lab. Terrorist groups have been known to post recipes on their Web sites.

Once made, people tend to use one of three methods for delivering their weapon. Often they'll conceal the device in a package that may be in plain sight, hidden or buried. Insurgents have even hidden IEDs in animal carcasses alongside military convoy routes. They may also place the IED in a vehicle's trunk (vehicle-borne IED or VBIED). A driver may park the vehicle alongside a convoy route. A remote watcher can then detonate the VBIED from a safe distance. The last delivery method relies on a suicide bomber. The suicide bomber may drive a VBIED into the target area and explode it or strap the device on his or her body, walk into the intended target area and explode it.

What happens when an IED explodes?

IED Impacts

Bryan Anderson, a U.S. Army military policeman, lost three limbs after an IED exploded near his Humvee in Iraq in October 2005.
Bryan Anderson, a U.S. Army military policeman, lost three limbs after an IED exploded near his Humvee in Iraq in October 2005.
Scott Olson/­Getty Images

Aside from how it's made, an IED is like any other bomb -- it explodes. Before you can understand the impact of an IED, it helps to know what's happening during that fateful moment.

  1. When the primary charge explodes, gases heat up and expand rapidly outward under pressure.
  2. The expansion creates shock waves or blast waves. The waves travel outward at about 1,600 feet per second (488 meters per second) over hundreds of yards or more depending upon the amount of explosive.
  3. The explosion fragments the container and sends pieces of shrapnel at high speeds outward. If the IED also contained other fragments such as ball bearings, nuts, bolts and pellets, then they also would be thrown outward.
  4. The heat from the explosion causes fire.
  5. The heat and fires from the explosion can cause secondary fires.
  6. The blast wave leaves a partial vacuum, which causes air to rush back in under high pressure. The inrushing air also pulls in debris and shrapnel.

­So, an IED explosion causes damage to vehicles and property primarily through the blast wave, heat and fires.

In contrast, casualties within the blast radius can stem from many causes. The explosion can release shrapnel or create debris from secondary impacts such as flying glass from broken windows. This debris can penetrate the body in many places, leading to lacerations, bleeding, broken bones and loss of limbs. Second, the heat from the blast causes fires; both the heat and the fires themselves can cause severe burns. Finally, the pressure in a blast wave can be on the order of 1,000 times atmospheric pressure. This intense pressure can rupture your eardrums and slam your brain against the inside of your skull, which leads to concussion, blindness, deafness and swelling of the brain. In addition, many air-filled tissues and organs such as the lungs and bowels can be perforated by the pressure changes.

The type and extent of the injury depends on the person's location relative to the IED. A person in the primary blast radius can be hit by pressure changes, heat and shrapnel. Most likely, this person will die. Outside the primary blast radius, a person is most likely to be injured by shrapnel. The person may survive depending on how many injuries the shrapnel causes and where they're located. If shrapnel tears a hole in a major artery, then that person can bleed to death.

­Civilian casualties are often high in IED attacks because these people are unprotected. Initial injuries to U.S. soldiers from IED attacks were caused mainly by shrapnel. However, the use of Kevlar body armor and helmets has greatly reduced shrapnel injuries. While these types of injuries have fallen, military surgeons have reported increases in traumatic brain injuries caused by the blast effects [source: Okie].

Defeating and Detecting IEDs

U.S. Army bomb team members watch the controlled detonation of an improvised explosive device (IED) to clear it from the streets in Baghdad, Iraq.
U.S. Army bomb team members watch the controlled detonation of an improvised explosive device (IED) to clear it from the streets in Baghdad, Iraq.
John Moore/­Getty Images

­Insurgents and terrorists don't just go make a bomb and use it. IED attacks are the result of coordinated enemy activities such as financing, obtaining supplies, making IEDs, and planting and detonating them. So defeating these devices must involve a combined strategy of understanding and observing the enemy. Soldiers and personnel have to be trained to be aware of the enemy's behaviors, to look for indicators of IEDs in their patrol areas and to use technology to dispose or disable them. The U.S. Army's IED defeat strategy includes the following measures:

  • Collecting data about enemy activities that might indicate upcoming IED attacks. This could be anything from observing suspicious activities of people within the combat area to tracing or disrupting the movements of supplies and money.
  • Detecting the IEDs themselves
  • Disposing of or disabling the detected IED
  • Protecting military personnel and civilians from a detected IED

Training soldiers to be keen observers in combat operations is important. For example, a U.S. Marine spotter near Habbaniyah, Iraq, noticed a man who was videotaping a nearby patrol of assault vehicles. The man had a high-powered rifle in his car next to him. After a sniper shot the man, soldiers discovered a cache of IED materials and munitions in the car.

A Category I (left) and Category II Mine Resistant, Ambush Protected vehicle (MRAP) drive through an off-road course during a demonstration in Aberdeen, Md. There's been a huge demand for the vehicles in Iraq.
Chip Somodevilla/­Getty Images

­Likewise, soldiers or other personnel should be trained to be suspicious of unattended packages along a road, fence, building or even a trash pile. IEDs are easy to hide. Simulating more IED attacks during military training will help soldiers to detect and deal with these attacks before encountering them in combat.

Besides training soldiers, some new technologies are capable of detecting, disrupting or disabling IEDs. These technologies are designed to place a "bubble" of protection around troops operating in combat situations. For example, many combat vehicles are now equipped with radio frequency jamming devices, which disrupt the cell phone signals often used to trigger IEDs.

Another device called a NIRF, which stands for neutralizing improvised explosive devices with radio frequency, emits a high frequency radio pulse that deactivates IED electronics within a short area. Microwave-pulsing devices also can be used to "fry" the electronics of IEDs. Another device called LIBS (laser-induced breakdown spectroscopy) uses lasers to detect IED explosives within a 100-foot (30-meter) radius.

Alternatively, you might not need a soldier to deal with a suspected IED at all. The military is exploring using robots and drones to protect people from IEDs. Aerial drones may be able to detect IEDs or suspicious activities without exposing troops, while robots can search areas for the suspected devices or handle shady looking packages without involving soldiers.

What about protecting soldiers during an attack if the detection methods fail? Kevlar body armor has shielded soldiers from the shrapnel released in an IED explosion. In addition, armored vehicles have been redesigned with the blast impacts of an IED in mind. These vehicles are called Mine Resistant Ambush Protected (MRAP) vehicles. Essentially, the usual flat undercarriage of a vehicle is changed to a V-shaped undercarriage, which diverts the blast waves from an explosion underneath around the vehicle rather than into it. Because IED attacks are a favored strategy in modern war, the U.S. Department of Defense continues research aimed at IED countermeasures.

Keep reading to learn more about modern warfare and military technology.

Related HowStuffWorks Articles

More Great Links


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