Experts quoted by the Washington Post think it almost certain the US military will use "high-powered microwave weapons" (HPM) against Iraq:

They use bursts of electromagnetic energy, delivered by low-impact bombs or "ray gun"-like devices, to disable or destroy the electronics that control everything from an enemy's radar to its laptops.

Although the pulse can easily incapacitate or even burn out microchips or circuitry, it is weak enough so that humans might not even know they had been attacked until their computers started to crash.

"These weapons are designed almost exclusively for destroying electronic systems," said defense analyst Loren Thompson, author of a recent study on high-powered microwaves and other "directed-energy" weapons. "They minimize collateral damage, overkilling and wasted effort. I tend to think this could make war more humane."

In particular, analysts point out, high-powered microwaves have an obvious attraction in an urban setting, where noncombatants are vulnerable. Iraqi President Saddam Hussein has concentrated his elite troops around Baghdad, apparently intending to make a U.S.-led invasion force its way into the capital.

Silent, invisible shivers of energy worming their way into bunkers and zapping the electronics of the enemy - the trouble is it cuts both ways:

From a military standpoint, the biggest drawback is the possibility that the pulses end up damaging friendly electronics as they rebound through a battlefield.

"Our existing military infrastructure is currently almost defenseless against the type of energy pulse that an HPM would produce," Thompson said. "The benefits of the information age created a vulnerability not only for our enemies, but for ourselves."

High-powered microwave weapons make use of the same principle that causes static to invade a car radio beneath a power line. More power on a frequency approximating that of the radio can cause progressively worse damage, and at some point will shut down or burn out delicate electronics. The armed forces describe the range of possibilities as the "four D's — deny, disrupt, damage or destroy."

"Anything that an enemy has that uses electronics could be vulnerable," said the University of New Mexico's Edl Schamiloglu, an electrical and computer engineer. "Radars, computers, infrared guidance systems — you name it."

The HPMs come in two flavors: "ultrawide band" and "narrow band":

ultrawide band ... uses an explosion to provide one quick, powerful burst of radiation over a broad range of frequencies. The likeliest method of delivery is via cruise missile, which can get the weapon close to the target without infecting friendly electronics.

....Once the waves are on their way, they will travel along any electrical circuit they encounter, and are particularly adept at taking advantage of enemy antennas and other devices as capable of receiving signals as they are of transmitting them. An antenna or other exposed sensor is called "the front door."

But it is not the only entrance. The emissions can also travel through cracks, seams, metal conduits or other "back door" avenues, crawling into hardened bunkers to disable electronics with a sudden, virtually undetectable power jolt. The microwaves will destroy the electronics even when the equipment is not operating.

....[narrow-band] characteristics are not publicly known, but Schamiloglu said machines rather than bombs would deliver them. All would likely have batteries as a power source, a large capacitor to store the power and an antenna to fire the microwaves in a rat-a-tat burst, ray-gun style.

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