The explosion that killed 14 marines in Haditha yesterday was powerful enough to flip the 25-ton amphibious assault vehicle they were riding in, like the one shown below left, in keeping with an increasingly deadly trend, American military officers say.
In recent months the roadside bombs favored by insurgents in Iraq have grown significantly in size and sophistication, the officers say, adding to their deadliness and defeating efforts to increase troops' safety by adding armor to vehicles.
The new problems facing the military were displayed more than a week earlier, on July 23, when a huge bomb buried on a road southwest of Baghdad Airport detonated an hour before dark underneath a Humvee carrying four American soldiers.
The explosive device was constructed from a bomb weighing 500 pounds or more that was meant to be dropped from an aircraft, according to military explosives experts, and was probably Russian in origin.
The blast left a crater 6 feet deep and nearly 17 feet wide. All that remained of the armored vehicle afterward was the twisted wreckage of the front end, a photograph taken by American officers at the scene showed. The four soldiers were killed.
And what happened in the aftermath of the July 23 attack provided further cause for alarm.
A British explosives expert, part of a special squad formed to investigate major insurgent bomb attacks, stepped on a second, smaller bomb buried near the first and was badly wounded, two American officers said. He later had an arm and a leg amputated. A third device, hidden a few yards away, was found and defused.
"This was a catastrophic event," said Sgt. Jason Knapp, an Air Force bomb technician who arrived at the scene of the multiple attacks the next morning. He found a foot from one of the American soldiers in the shallow water of a nearby canal. "It was pretty disturbing," he said.
Military personnel involved said the attack last month indicated to them that a new and deadly bomb-making cell singling out American patrols was operating near the large allied military base at the airport, an area that two officers said had seen little insurgent activity in months.
There was further evidence for that on Saturday. Less than a mile from the July 23 attack, four more American soldiers were killed when their Humvee was struck by another hidden bomb.
From the earliest days of the insurgency there has been a constantly evolving battle of wits between insurgent bombers and soldiers trying to stop the roadside bombs and suicide attacks.
As the threat from bombs and suicide attacks has grown, the Pentagon has rushed 24,000 armored Humvees to Iraq since late 2003. But the insurgents have responded by building bombs powerful enough to penetrate the vehicles' steel plating.
Senior American commanders say they have also seen evidence that insurgents are making increased use of "shaped" charges, which concentrate the blast and give it a better chance of penetrating armored vehicles, causing higher casualties.
Bomb-making techniques used by the anti-Israeli militant group Hezbollah in Lebanon have increasingly begun appearing in roadside bombs in Iraq. A senior American commander said bombs using shaped charges closely matched the bombs that Hezbollah used against Israel.
"Our assessment is that they are probably going off to school" to learn how to make bombs that can destroy armored vehicles, the officer said.
As the military has begun conducting post-bombing investigations, insurgents have increasingly been planting multiple devices at the same location, apparently to disrupt investigative teams sent to the blast site, or at least delay their work while they clear the site of any secondary bombs.
Sometimes improvised explosive devices, known as I.E.D.'s, are placed in the open to draw in American disposal units. "A lot of times they plant fake I.E.D.'s and wait until you come on site to open up," said Sgt. Burnell Zachary. "Once the mortar rounds stop, the drive-bys come."
Last week, as an American bomb team was defusing a bomb in the predominantly Sunni Arab neighborhood of Amiriya in Baghdad, a passing black BMW opened fire on the unit and its security detail, according to an after-action report. An Iraqi police detachment that was providing security for the team returned fire and struck the passenger in the car in the chest, the report said.
A few blocks away, American snipers were watching an Iraqi man who was stacking rocks along a street that the bomb disposal unit would drive down as it was leaving the neighborhood, according to the report. They suspected that he was building a hiding place for a bomb.
"Snipers engaged and killed the individual, who appeared to be emplacing an I.E.D.," the report says.
At best, American soldiers familiar with the bomb problem say, they may be able to reduce the number of attacks, which average around 65 a day against Iraqis and Americans troops, and hand over the fight to Iraqi security forces sometime next year.
"It's not realistic to think we will stop this," says Sgt. Daniel McDonnell, who leads a three-man team of explosives technicians responsible for finding and defusing improvised explosive devices in Baghdad. "We're fighting an enemy that goes home at night and doesn't wear uniforms. But we can get it to an acceptable level."
Americans directly engaged in the fight say that while they are having some success at tracking down some of the perpetrators, there is a steady supply of Iraqis willing to set bombs for a small amount of money.
At least four Army bomb technicians have been killed by such hidden bombs this year, according to Capt. Gregory Hirschey, a company commander in the 717th Explosive Ordinance Disposal Battalion.