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Robert Maginnis, a military analyst and Army adviser, said IEDs are tailor-made for Afghanistan.

“IEDs are effective in Afghanistan in part because of the terrain,” Mr. Maginnis said. “There are few paved roads, which means planting a device in or near a road is easier and harder to detect by visual inspection. The increase in Taliban use of IEDs is due to the increased coalition forces in country, which forced the relatively small Taliban force to adjust its tactics. It stretches the force’s impact.”

Lt. Col. Edward Sholtis, a spokesman for Gen. Stanley McChrystral, the top commander in Afghanistan, told The Times the general has stepped up efforts to disrupt networks before they can plant bombs, and get better intelligence on where they are embedded in light of “the weapons’ increasing use against coalition forces and because of the impact of a larger number of indiscriminate, victim-operated IEDs on the Afghan people.”

“Like most everything in Afghanistan, the IED threat here is complex, and we go about addressing it in a number of ways,” Col. Sholtis said. “Broadly speaking, there’s an offensive component that involves intelligence collection tied to Afghan and coalition operations designed to identify and disrupt the cells that manufacture, place and operate IEDs.

“There’s also a robust defensive component that involves a comprehensive reporting system that tracks IED events, disseminates threat intelligence to all levels, identifies emerging threats and lessons learned, and trains the force in the latest threats and countermeasures.”

Two nonmetallic ingredients, salt solution and carbon, are being considered by the Taliban as IED trigger mechanisms, the Pentagon report said. The Taliban can harvest carbon from everyday batteries. This reduces the amount of metal, making detection difficult.

“The use of IEDs as antipersonnel mines offers several distinct advantages,” the report said. “They are small and easily transported and emplaced. They are easily camouflaged and do not need to be remotely controlled. In addition, antipersonnel IEDs are almost always lethal to their victims and are extremely difficult to detect with current U.S. minesweepers.”

One Taliban tactic involves waiting until NATO forces enter an IED field. Once a bomb explodes, the militants open fire with mortars and rocket grenades.

The military source said the Taliban is also thwarting detection by using long pull-cords rather than an electronic signal to ignite IEDs. This way, the bomb cannot be defeated by electronic countermeasures on vehicles and aircraft that jam the signal.

The source, who completed several tours in Afghanistan, said the Taliban strategy has been to abandon some villages rather than fight the Marines head-on. They then watch the Marines’ routines and place IEDs along those routes.

The Pentagon report said the current mine detector, the AN/PSS-12, is not sufficiently sensitive to pick up the scarce metal in anti-personnel IEDs. “There is an urgent need to identify new man-portable detection platforms to expand the ability of U.S. troops to detect anti-personnel IED-mines,” the report concludes.

One system now readily available commercially consists of electric field sensors, which can pick up electricity from nonmetallic conductors, the report said.