'If you don't go after the network, you're never going to stop these guys. Never.'

In some instances, according to a senior officer in Baghdad, investigations of fatal IED attacks revealed that "the device that killed them was triggered by a frequency that could have been stopped by proper jamming." A now-retired Army lieutenant colonel said, "There were a whole lot of things that made you just want to cry."

Among the biggest problems was simply the crowded electromagnetic environment in Iraq. Most fiber-optic and above-ground telephone lines had either been destroyed during the 2003 invasion or subsequently looted by copper-wire scavengers. Now 27 million Iraqis used unregulated cellphones, walkie-talkies, satellite phones, long-distance cordless phones and, in hundreds of instances each month, radio-controlled bombs.

About 150,000 coalition troops also sent out a great spray of electronic emissions, which mutated dramatically every time new equipment or a new contingent of soldiers arrived, including some with old Warsaw Pact electronics. "People have said it's the most challenging electromagnetic place in the world," a Navy captain said. "It's very complex." Trying to make sense of the signals, he added, was "like having your head underwater."

This was especially true in Baghdad, where the electromagnetic environment seemed to vary between neighborhoods, between seasons, between times of day. "No one realized," the senior Pentagon official said, "how much tougher jamming was going to be in the ground plane" -- the ground-air interface, where earth meets sky. The Army logistician added: "We didn't scientifically map out the problem set, so we didn't know the normal electronic noise of a taxi driver doing his thing, the doorbells, the garage door openers, the satellite communications. . . . You have to know the normal program of life."

The Pentagon would spend millions of dollars trying to replicate Baghdad's idiosyncratic airwaves in laboratories and at Yuma Proving Ground in Arizona. Senior commanders in Baghdad "were going bonkers," the Army colonel recalled. "They were saying, 'How do we fix this?' "

Worse yet, there were problems with Duke, the sophisticated reactive jammer the Pentagon had decided would replace the various models being used in Iraq. Syracuse Research Corp., a not-for-profit company created by Syracuse University in 1957, had won the competition for Duke using design concepts developed by Army engineers at Fort Monmouth, N.J. The contract was signed in June 2005, with the first Duke -- a big box with a big antenna -- completed in November. But deployment to Iraq was delayed to allow adjustments and more tests.

This state of affairs pleased no one, but it particularly displeased the Marine Corps. Marine casualties had been severe in Anbar province, where high-powered radio-controlled IEDs were pernicious. Some Marine officers also feared that they could be shortchanged as Dukes reached the field, that the Army was "taking all the good stuff," as one source put it. "The issue got ugly with recriminations."

"It was part service rivalry, part delivery schedules, and partly that no one could make stuff fast enough," said Macy, the rear admiral. "You can't walk into Circuit City and say, 'I want 25,000 high-powered jammers.' "

The Marines had already hedged their bets. Med-Eng Systems, a Canadian firm, made an active jammer that worked by "blasting away, locking up everything," according to a retired Navy captain. As a foreign firm, Med-Eng needed a U.S. partner to work on classified programs. Soon a corporate marriage was arranged with General Dynamics Armament and Technical Products in Charlotte.

If inelegant, the jammer had showed promise in tests conducted in the summer of 2005. Because it could be reprogrammed to meet changing insurgent threats, from key fobs to cellphones, the gadget was named Chameleon.

The Marines bought 1,000 Chameleons in November 2005. After encouraging tests at Johns Hopkins University Applied Physics Laboratory and elsewhere, the Marines announced on Feb. 8, 2006, a $289 million contract that increased the purchase to 4,000 Chameleons, which later grew to 10,000.

Explosive ordnance teams use the Mini-Andros II mobile robot to help disarm roadside bombs.

General Dynamics threw its considerable heft into the project, even using a corporate jet as a delivery van to pick up components nationwide, according to company sources. "Marines take care of their own," a General Dynamics talking point advised, but the company also eyed a bigger prize. The first Dukes had deployed overseas in February 2006, yet the jammers' difficulties in Iraq's electromagnetic environment persisted.