AMMUNITION SUPPLY POINT WOLF, Iraq – Fourteen Marines killed Wednesday in western Iraq were en route to retake an area that had been cleared of insurgents at least once before when their lightly armored amphibious assault vehicle was blown apart by an insurgent-laid roadside bomb.

Pentagon officials said they knew few details of the explosion, the deadliest roadside bombing of a U.S. combat vehicle since the war began. Officials in Washington said they didn’t know whether the explosion was caused by a mine or by an improvised explosive device, or IED, jury-rigged from castoff munitions. IEDs have become the No. 1 cause of death for American troops in Iraq.

But the explosion, in western Anbar province near Iraq’s border with Syria, underscored two realities American forces face as they attempt to quell insurgents:

First, U.S. troops continue to face ever more powerful roadside explosives that have defied U.S. countermeasures. In the past two weeks, at least 31 U.S. soldiers and Marines died in roadside bombings, including explosions that struck Humvees that had additional armor and Bradley Fighting Vehicles, which are more heavily armored than the assault vehicle the Marines were riding in Wednesday.

Second, insurgents remain a potent force in western Iraq despite at least five battalion-sized operations launched since May to quell Iraq’s increasingly bloody insurgency.

“Just because you take a town doesn’t mean it will stay quiet,” said Marine Col. Stephen Davis, commander of the Marine Regimental Combat Team overseeing western Anbar.

Marines here expressed frustration. “We roll into a town, we clear it out, we deem it clear,” said Staff Sgt. John Allnut, 36, of Washington, D.C. “But you know that the second you leave, within hours or days, there’s going to be activity, or they’re going to go back in there.”

Wednesday’s attack occurred about an hour east of this dusty supply depot, near the town of Haditha. It was the second fatal attack on Marines near Haditha this week. On Monday, six Marines on foot patrol in the area were killed after they came under small-arms fire.

The Marines, all members of the 3rd Battalion, 25th Marines, based in Brook Park, Ohio, were on their way to assault insurgent positions when their amphibious assault vehicle rolled over the explosives.

Fourteen were killed, nine of them from a single unit based in Columbus, Ohio. The men’s civilian interpreter also was killed. A 15th Marine escaped, reportedly scrambling from beneath the vehicle’s wreckage.

Cpl. Adam Babin, 21, of North Yarmouth, Maine, said he was surprised Haditha was again a source of trouble for the Marines.

“We detained a bunch of guys out in Haditha, and for a while the mortars there stopped,” he said. “Everyone was pretty much under the impression with Haditha that we’d cleaned the area out. And now this happens, and you’re back at square one.”

Officials in Washington acknowledged that the Marines were riding in a vehicle designed 40 years ago for a different kind of warfare – the beach assaults the Marines made famous at Iwo Jima and elsewhere in the Pacific during World War II.

The AAVP7A1 “Armored Assault Amphibious Fully-Tracked Landing Vehicle” is essentially a modern variant of the WWII model, designed to carry troops from ship to shore and for use in land operations, according to a Marine Corps fact sheet. It travels at about 6 mph through surf and sand and can cruise at about 20 mph on land.

But those kinds of missions were “combined-arms” assaults, backed by heavy amounts of air, ship and artillery support, said Daniel Goure, a military analyst at The Lexington Institute, a policy group based in Alexandria, Va.

The vehicle wasn’t designed to engage in the kind of day-to-day patrolling of insurgent-controlled territory that the Marines are doing in western Iraq. During the initial assault into Iraq, many of the vehicles broke down on the long drive to Baghdad and had to be towed by other vehicles.

“It is very lightly armored. It is under-powered. It is essentially a big boat on land, and that makes it vulnerable,” said Goure. “It was never intended for these kind of missions. It was never designed for the kind of beating it has been getting.”

While many lawmakers have been clamoring for the Pentagon to add more armor to vehicles in Iraq to counter bombs, Goure said the issue isn’t that simple.

“There are not enough main battle tanks in the world to equip the forces in Iraq,” he said. “There is no way to equip these forces to withstand a direct hit from a 1,000- to 2,000-pound IED.”

Insurgents have proved adept in recent days in attacking far more heavily armored vehicles. In the past two weeks, at least 31 U.S. soldiers and Marines have died in roadside bombings. At least three of the bombings that killed soldiers involved armored Humvees, including two incidents that killed eight members of the Georgia National Guard’s 48th Combat Brigade Task Force.

Five soldiers were killed in two separate incidents involving Bradley Fighting Vehicles, the military’s most heavily armored infantry carrier.

‘Lethality high’

U.S. Army Brig. Gen. Carter Ham, who once commanded U.S. forces in Mosul and is now deputy director of operations for the Joint Chiefs of Staff, said the number of roadside bombings had dropped in recent months, but that in each incident, “the lethality has remained very, very high.”

“We are seeing larger amounts of explosives,” he said.

Bombs claimed the lives of 39 U.S. and allied troops in Iraq in July, the highest monthly total since the war began nearly two and half years ago. Of those deaths, 36 were Americans, capping a three-month trend in which IEDs were the No. 1 cause of U.S. casualties. The figures were compiled by Iraq Coalition Casualty Count, a Web site that compiles statistics on U.S. and allied casualties based on Defense Department press releases and media reports.

Earlier this week, a spokesman for the Pentagon’s Joint IED Task Force, which is charged with devising tactics and evaluating countermeasures against the bombs, said recent trends indicate insurgents are becoming more adept at using explosives.

“The terrorists are now using larger, more powerful IEDs, and they are attacking the undercarriages of our vehicles now, where the armor is not as thick as on the sides,” said spokesman Richard Bridges. “They are also, in some instances, using home-engineered shaped-charges that are more effective at penetrating armor.”

Ham said much the same Wednesday in Washington: “This is a very brutal, lethal and adaptive enemy.”

(Lasseter reported from Ammunition Supply Point Wolf, Brown from Washington. Knight Ridder Newspapers correspondent Richard Chin of the St. Paul Pioneer Press contributed to this report from Baghdad.)

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