How IEDs Work

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

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:

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:

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?

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.

­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].

­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:

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.

­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.