WASHINGTON, June 21 – American casualties from bomb attacks in Iraq have reached new heights in the last two months as insurgents have begun to deploy devices that leave armored vehicles increasingly vulnerable, according to military records.
Last month there were about 700 attacks against American forces using so-called improvised explosive devices, or I.E.D.’s, the highest number since the invasion of Iraq in 2003, according to the American military command in Iraq and a senior Pentagon military official. Attacks on Iraqis also reached unprecedented levels, Lt. Gen. John Vines, a senior American ground commander in Iraq, told reporters on Tuesday.
The surge in attacks, the officials say, has coincided with the appearance of significant advancements in bomb design, including the use of “shaped” charges that concentrate the blast and give it a better chance of penetrating armored vehicles, causing higher casualties.
Another change, a senior military officer said, has been the detonation of explosives by infrared lasers, an innovation aimed at bypassing electronic jammers used to block radio-wave detonators.
I.E.D.’s of all types caused 33 American deaths in May, and there have been at least 35 fatalities so far in June, the highest toll over a two-month period, according to statistics assembled by Iraq Coalition Casualty Count, a Web site that tracks official figures.
In a sign of heightened American concern, the Army convened a conference last week at Fort Irwin, in the California desert, where engineers, contractors and senior officers grappled with the problems posed by the new bombs. One attendee, Col. Bob Davis, an Army explosives expert, called the new elements in some bombs “pretty disturbing.” In a brief interview, he declined to discuss the changes, but said the “sophistication is increasing and it will increase further.”
Although the number of bombs using the refinements remains low, their appearance underscores the insurgents’ adaptability and the difficulty the Pentagon faces, despite a strong effort, in containing the threat. Improvised explosives now account for about 70 percent of American casualties in Iraq.
At a briefing on Tuesday for reporters at the Pentagon, General Vines, who spoke by telephone from Iraq, said that the insurgents’ tactics “have become more sophisticated in some cases,” and that they were probably drawing on bomb-making experts from outside Iraq and from the old Iraqi Army. He added that the insurgency was “quite small” and “relatively static,” a view not shared by all his colleagues.
Car bomb attacks against American forces – both suicide attacks and attacks with remotely detonated devices – reached a monthly high of 70 in April and fell slightly in May, according to figures provided by the United States military in Iraq.
“For a period of time we felt we were pushing them away from us, and now it looks like they are back to targeting coalition forces,” said a Pentagon official involved in the anti-I.E.D. effort. “And they’ve learned that in order to attack us, they need to get more sophisticated.”
The next highest two-month period was in January and February, around the time of the Iraqi elections, when 54 Americans were killed by bombs, according to the official statistics assembled by the casualty-count Web site. Iraqis suffer the most casualties by far, though reliable figures are not available.
The insurgents “certainly appear to be surging right now,” Brig. Gen. Joseph L. Votel, who leads the anti-I.E.D. task force, said in an interview at Fort Irwin. “Time will tell about their ability to sustain this.”
American officials also worry that the increase in attacks threatens to disrupt Iraq’s fledgling government further and could threaten the Bush administration’s strategy for maintaining public support for the American presence in Iraq by holding down American casualties.
“We’re in a very, very dangerous period,” said a senior military official at the Pentagon. “To be a successful insurgent you need to be able to create spectacular attacks, and they’ve certainly done that in the past several weeks.”
In addition to technical improvements in their bombs, insurgents, especially in rural areas, are resorting to packing more explosives into the devices to disable armored vehicles, Army experts at the Fort Irwin conference said.
Hundreds of armored Humvees have been rushed to Iraq over the past year, and Pentagon officials say unarmored vehicles are now confined to bases. Still, five marines were killed this week near Ramadi, about 70 miles west of Baghdad, when their vehicle hit an I.E.D. Earlier this month, five marines were killed after their vehicle struck a bomb in Haqlaniya, about 150 miles northwest of Baghdad.
A senior Marine officer with access to classified reports from the field said that the vehicles involved in the two fatal attacks were armored Humvees but that the bombs “were so big that there was little left of the Humvees that were hit.”
Insurgents have long been able to build bombs powerful enough to penetrate some armored vehicles. But the use of “shaped” charges could raise the threat considerably, military officials said. Since last month, at least three such bombs have been found, Lt. Gen. James T. Conway, the director of operations for the Joint Chiefs of Staff, told reporters at a Pentagon briefing this month.
The shaped charge explosion fires a projectile “at a very rapid rate, sufficient to penetrate certain levels of armor,” General Conway said, adding that weapons employing shaped charges had caused American casualties in the last two months. He did not give details.
A Pentagon official involved in combating the devices said shaped charges seen so far appeared crude but required considerable expertise, suggesting insurgents were able to draw on well-trained bomb-makers, possibly even rocket scientists from the former government. Shaped charges and rocket engines are similar, the official said.
Infrared detonators are an advance over the more common method of rigging bombs to explode after an insurgent nearby presses a button on a cell phone, a garage-door opener or other device that gives off an electric signal. That approach is vulnerable to jammers, however, and a shift to infrared detonators, which rely on light waves, underscores the insurgents’ resourcefulness.