Insurgents Using U.S. Techniques

"Once you transfer this basic methodology, it lives forever and people build on it," Lang said. "That's one of the arguments for not making the transfers in the first place."

A copy of the Iraqi manual was made available to The Washington Post by Tim Brown, a senior fellow at GlobalSecurity.org, who said he found it several years ago while rummaging around a military surplus store in Los Angeles. He recognized its similarity to the U.S. manual, which he said he had obtained years earlier at a gun show.

Roadside bombs -- the military calls them "improvised explosive devices," or IEDs -- continue to rank as the number one killer of U.S. troops in Iraq, according to Pentagon figures. About half of all combat casualties in Iraq are attributed to them.

Countering them has become a top Pentagon priority. At the Army's Communications-Electronics Command here, more than 80 engineers and other specialists are engaged in the effort. Throughout the military, dozens more also are working on the problem, with hundreds of millions of dollars now devoted to the project, defense officials said.

"This is a long-term threat, not just to our armed forces but I think to our citizens," Gordon R. England told a Senate panel last week at a hearing on his nomination to become deputy secretary of defense. "If there's ever an attack, it will be this kind of attack -- or potentially this kind of an attack -- in America."

England said there have been discussions with the White House, the national academies of engineering and science, and others to undertake "some fundamental research across America" aimed at defeating the threat.

In recent months, the U.S. military has employed different ground-based and airborne jamming devices with some success at thwarting roadside bombs. One set of jammers, known as the Warlock series, emits radio frequencies to interfere with the signals used to detonate IEDs. These devices are modified versions of a system known as Shortstop that was devised to explode incoming artillery and mortar rounds before they struck.

According to Army figures, about 30 to 40 percent of IEDs are now found and rendered safe, and those that do go off are causing fewer casualties. But the number of IED incidents has steadily climbed and currently exceeds 30 a day, the Army says.

The devices are becoming increasingly sophisticated as U.S. specialists find ways to jam them. Early models, which relied on such triggers as garage door openers, wireless doorbells and car alarm remotes, have given way to ones detonated by cell phones and other devices with more complicated frequencies.

U.S. officials here with access to intelligence reports on insurgent tactics said no single bombmaking mastermind appears to exist in Iraq. Rather, they said, the bombs being made appear to reflect the signatures of various regional designers.

"It's still all over the map, how they build these things, depending on their level of training," the senior official said.

While the detonating devices vary, the types of explosives used tend to be predictable, consisting largely of dynamite, land mines or old artillery shells. U.S. investigators have uncovered no sign of more powerful munitions, such as HMX or RDX. The disappearance of nearly 400 tons of these explosives from Iraq's Qaqaa weapons facility shortly after the U.S.-led invasion in 2003 caused a stir last October when it was revealed, raising speculation that the material could find its way into IEDs against U.S. and allied troops.

"Electronic warfare is often referred to as a chess game, and EW players are called knights of the chessboard because they have the ability to jump over others," the official here said. "It's a game that goes on forever. When we defeat one method, a smart enemy will move on to something else."

Priest reported from Washington.