Improvised explosive devices -- IEDs for short -- are the weapons of choice for Iraqi insurgents, with triggers that can be improvised from an easy-to-find object, such as a phone or even a remote-controlled toy.
Today's attack that injured "World News Tonight" co-anchor Bob Woodruff and cameraman Doug Vogt was part of a surge of roadside bombings in Iraq. There were approximately 10,600 roadside bombings in 2005, nearly double the number of attacks that occurred in 2004.
Such attacks have accounted for more than half of all U.S. military injuries in Iraq. They are, by far, the single-greatest cause of death for U.S. service members.
Abundant Explosives and Ingenuity
The explosives for the IEDs are easy to find because Iraq stockpiled 650,000 tons of ammunition before the war.
In addition, ingenuity and experience have helped the insurgents fashion ever-more-lethal devices, including bombs with nails and ball bearings, intended to maim and kill, and shape charges, designed to cut through steel armor plates.
Often, when insurgents plant an IED, they watch and wait to trigger the bomb when it will inflict maximum damage. Often, they film the results.
Vogt filmed an IED attack just last month. He was in Iraq for "Nightline" when another convoy he was in hit an IED. That day, he did not suffer any injuries.
Across Iraq, more than 200 IED attacks were reported last week alone. On average, that's more than 30 a day.
The U.S. military has had to adapt its tactics. So-called "hillbilly armor" -- improvised from Kevlar vests in some cases -- shores up their Achilles' heels.
Deterring IED attacks is a central focus of U.S. military officials. Defense Secretary Donald Rumsfeld recently expanded the Joint IED Defeat Team and has established a special center in the Mojave Desert devoted to learning more about IEDs and how to stop them.
Iraqis Are Targets
Iraqi soldiers are among the most vulnerable because in general the vehicles they drive are not armored.
Woodruff and Vogt were traveling with Iraqi troops when their convoy was hit with an IED.
This weekend, ABC News spoke with Iraqi troops north of Baghdad, not far from where today's attack took place. They said they often feel like sitting ducks.
"The other day a bomb hit our vehicle," one soldier said through a translator. "If we had been in an American Humvee, you wouldn't see much damage. But check out that car: It's totally destroyed."
Though the number of IED attacks on U.S. and coalition forces continues to climb, there are fewer fatalities from the attacks.
Perhaps that's because each successive deployment of soldiers learns from the last how to become more "situationally aware." Also, equipment is more effectively hardened. And commanders learn how to best move troops around the "battle space" in ways that are meant to limit the effectiveness of IEDs.
In Baghdad, every single journalist is well aware that every time they are out on the streets, they're at risk of an IED attack. Woodruff and Vogt knew that too; they both have lots of experience in war zones. But it's a risk journalists take in order to cover the story.
ABC News' David Wright in Baghdad and Brian Hartman in Washington contributed to this report.