After 31 months of fighting in Iraq, more than half of all American fatalities are now being caused by powerful roadside bombs that blast fiery, lethal shrapnel into the cabins of armored vehicles, confronting every patrol with an unseen, menacing adversary that is accelerating the U.S. death toll.
U.S. military officials, analysts and militants themselves say insurgents have learned to adapt to U.S. defensive measures by using bigger, more sophisticated and better-concealed bombs known officially as improvised explosive devices, or IEDs. They are sometimes made with multiple artillery shells and Iranian TNT, sometimes disguised as bricks, boosted with rocket propellant, and detonated by a cell phone or a garage door opener.
The bombs range from massive explosives capable of destroying five-ton vehicles to precision "shaped charges" that bore softball-size holes through thick armor, the main defense of troops in the field, and they are becoming a key factor in the fast-rising U.S. death toll.
It took about 18 months from the start of the March 2003 invasion of Iraq to reach 1,000 U.S. deaths; it took less than 13 months to reach 1,000 more. A major reason for the surge, statistics show, is the insurgency's embrace of IEDs, together with the military's inability to detect them.
"It's the dreaded IED that's killing our soldiers," said Michael White, the creator of icasualties.org, a Web site that tracks U.S. military casualties. "I read in the paper that we have some new device to detect them, or we're taking extra care to make sure we don't get hit, and death after death keeps coming in, and it's IEDs."
In the first six months of battle in Iraq, only 11 soldiers -- about 4 percent of the 289 who died -- were killed by homemade roadside bombs. In the last six months, at least 214 service members have been killed by IEDs, or 63 percent of the 339 combat-related deaths and 53 percent of the 400 U.S. fatalities, according to data complied by the Brookings Institution's Iraq Index.
"The IEDs are the biggest threat we have," said Lt. Col. John Walsh, commander of Task Force 1-163, a Montana Army National Guard battalion that is completing a year-long combat tour in Hawija, a Sunni Arab city about 30 miles southwest of Kirkuk. Walsh's soldiers have encountered more than 600 roadside bombs, 60 percent of which exploded before they were detected. The unit has lost four soldiers, two from roadside bombs, and had 68 wounded, a casualty rate of 8.5 percent.
"Right now they're probably four times more powerful than when we first got here," 1st Sgt. Stanley Clinton said, referring to the bombs. Clinton, 53, has been deployed for the past year in Kirkuk for Alpha Company of the 2nd Battalion, 116th Brigade Combat Team.
Clinton said that when the 116th combat team, an Idaho Army National Guard unit, arrived last December, the insurgents employed "backwoodsy stuff" -- often tiny bombs fashioned from items as basic as Coca-Cola cans. Now, he said, they often consist of one or more 120- or 155-mm artillery rounds, 15 or 20 pounds of rocket propellant or shaped charges that concentrate the blast and punch through armor plating.
"Clearly we are not winning the competition over tactics and counter-tactics," said Michael O'Hanlon, a defense analyst who heads Brookings' Iraq Index. "The insurgency's ability to hide IEDs better, detonate them more remotely and build them more powerfully has been at least as effective as our improvements in better armor and better tactics."
In some instances, insurgents have constructed IEDs powerful enough to kill soldiers inside 22-ton Bradley Fighting Vehicles, which are more heavily armored than Humvees.
Even though U.S. commanders have placed huge emphasis on countering IEDs, O'Hanlon said, "We are still suffering as many casualties as ever, which makes me wonder if we've found the limitations of our reconnaissance measures." Militants may have discovered, for instance, how to avoid being spotted by surveillance flights, he said.
The development of shaped charges appears to be a direct response by insurgents to the Americans' use of more heavily armored vehicles, according to soldiers and U.S. military explosives experts. Those vehicles -- principally five-ton, armor-plated Humvees -- are used by all U.S troops traveling outside military bases. The Pentagon drew criticism last year for failing to provide adequate protection for soldiers patrolling Iraq's increasingly dangerous streets.
To fashion a shaped charge, one end of a cylindrical object such as a pipe is welded shut, and is then packed with explosive material and a conical piece of metal that becomes a molten projectile when the device is detonated. The charge is designed to focus the blast on a small area. In the case of a Humvee, the charge blasts a hole in the armor plating, propelling the scorching metal into the vehicle's cabin.
In July, a Humvee belonging to Alpha Company was out on patrol in Kirkuk when it was hit by a bomb equipped with a shaped charge, said Capt. Paul White, 39, the company commander. The explosion drilled a hole the size of a softball in the driver's door, he said. The red-hot shrapnel severed the driver's legs while the Humvee was still moving.
"He probably would have bled out except the shaped charge made [the metal] so hot it actually cauterized his legs as it cut his legs off," White said.
When a soldier yelled to stop the vehicle, White said the driver replied: "I can't stop. I don't have any legs."
"He literally said that," White recalled, adding that the Humvee came to a halt only after it rammed into a store.
According to a former Iraqi army officer who lives in the insurgent stronghold of Ramadi and is now a member of al Qaeda in Iraq, the group headed by Abu Musab Zarqawi, insurgents have advanced beyond the crude bombs they once used, such as dynamite or gunpowder mixed with nails and buried beside a road. Now, he said in an interview, militants have access to TNT from Iran that he said was about seven times stronger than the TNT available in Iraq. He said they were also using old Austrian missiles from the former Iraqi army and detonating them with electric wires, cell phones and other remote-control devices.
An Oct. 15 IED attack on a U.S. convoy in the village of Albu Faraj, just east of Ramadi, illustrated some of the new methods.
Haj Ali Eedan, 52, a farmer who watched the operation, said armed men planted a cylinder that looked like a hospital oxygen tank near a road, then moved it twice before finally hiding it in a pile of discarded nylon baskets. His son, Hussein, 30, said he thought the final site was selected for a reason other than that the cylinder would be well-hidden there.
"They were trying to find a solid place -- like metal, iron, or concrete -- to put the IED on," he said. "This makes the explosion three times more powerful than burying it."
The deadliest such attack came in August, when 14 Marines and an Iraqi civilian died in a single blast near Haditha, 125 miles northwest of Baghdad. The military later said insurgents had detonated a stack of three antitank rounds under an amphibious assault vehicle, the moderately armored personnel carrier used by Marines.
"We got better armor, they started getting better ordnance," Col. Bob Chase, the operations chief for the 2nd Marine Division, based in Ramadi, said at the time.
The insurgents have hidden the bombs in gunny sacks to disguise them as part of the garbage that litters the streets of Kirkuk, soldiers said. They have embedded them in concrete blocks similar to those used as building materials in new Kurdish settlements. As the Americans adapt their tactics, so, too, do the insurgents.
On the night of their Baghdad patrol this week, a platoon from the Army's 4-64 Armor Battalion of the 3rd Infantry Division studied every pile of trash on the side of darkened streets for telltale wires and other signs of explosives.
Earlier in the war, "We had an enemy who we could see," said Sgt. Brian Zamiska, 27, of Bentleyville, Pa., tapping the hood of a black Opel sedan as the patrol passed it. "We didn't have to worry about looking at every cardboard box in the road or every car like this and wondering if it was going to blow up."
His platoon mate, Lt. Lennie Fort, 30, of Clarksville, Tenn., said this style of warfare was frustrating.
"There's no one to shoot back [at], no one to kill," he said. "Honestly, it just gets us amped up to go out and get someone, but there's never anyone to get."
"Now they get a hose and they lay it across the road, and when you drive across it, it ignites the IED," said Clinton, the Alpha Company sergeant in Kirkuk. "You know years ago, when you had service stations where you'd drive across the rubber hose and it would go, 'ding, ding, ding'? Here you drive across a little hose and it sends water back into a little bottle with wires sitting there. When water goes back into the bottle, it connects wires, and off goes the IED. It's just so simple and so stupid."
Fainaru reported from Kirkuk.
An unexploded IED sits on the hood of a car as American soldiers investigate at the site of an April attack on a U.S. convoy north of Baghdad.