Outside Baghdad, a close encounter with a roadside bomb

Marines setting out at night to engage Iraqi insurgents get waylaid by a hidden explosive and call in back up to defuse it.

Attacked four nights in a row while on patrol in this hostile town, US marines rolled out late Tuesday, deliberately preparing to pick a fight.

But instead of targeting the Americans with bullets and grenades, Iraqi insurgents laid another surprise: A softly blinking blue cellphone hidden in a bush, wired and taped as a detonator, and linked to a long red detonation cord that disappeared into the cab of a burned-out oil tanker on the side of the road.

Waiting to blow inside: three 130mm artillery shells, daisy-chained to explode simultaneously .

The cellphone needed only a call to trigger the explosion.

The next American target that would pass were the six vehicles and 31 marines of the Alpha Company, 1st Battalion 2nd Marines, with lights dimmed and weaponry primed.

The likelihood of finding this improvised explosive device (IED) in the dark and on the traffic-laden north-south Highway 8 - which US patrols usually speed along - may have been even less than finding the proverbial needle in a haystack.

But find it they did, as the convoy serendipitously steered for a moment into the oncoming lane and halted close to the IED. Marines dismounted and used flashlights for a random search of their perimeter - and spied the blinking phone and the detonation cord.

"That's the Holy Ghost for you," said 2nd Lt. Mark Nicholson, the platoon commander, as he ordered traffic halted in both directions and razor-wire barriers set up. These marines, who have almost daily experience with the IEDs - either blowing up or being discovered - grumbled that their plans to draw out an attack were now off.

"This just gets to be a nuisance," said Lieutenant Nicholson, angry too that the anticipated firefight was unlikely to happen.

"Have you ever been hit by an IED? It's crazy," says Nicholson. "We all have [been hit], sometimes more than once a day."

The platoon commander tells of one day not long ago - before the 1-2 Marines seized two large weapons caches in the area - when his patrol was on the troubled west side of the Euphrates River. The first IED tore away the fingers of one marine and killed a civilian. Then the marines hit another IED as they were being relieved.

"Everyone said, 'Whew, we made it!' and all the rest of that night and the next day we got mortared," says Nicholson. "They on the way back, we hit a [car bomb]. There was nothing left but a motor and a disk brake drum - that was it. It blew a track [armored vehicle] off the road, and my platoon sergeant had to be evacuated."

Upon finding this IED, Nicholson radioed for an explosives ordnance disposal (EOD) team, to examine the bomb and make it safe. Marines took defensive positions, almost certainly under the eye of the would-be bomber. A smattering of residences and hole-in-the-wall businesses lined both sides of the highway.

"Someone is watching us right now," said Nicholson, referring to the bomber. "Take great care. Night is the worst time for IEDs."

The EOD team arrived with a powerful marine armored security detail: 10 vehicles in all, packing antitank weapons and high-caliber guns - almost too powerful for some from Alpha Company.

"Warn your marines!" said the security detail chief. "If we receive any fire, we are laying down 2,000 to 3,000 rounds, before we even dismount. If we start, you guys should just take cover until we're done."

The marine then shot out several street lights so the large assembly of Americans would not make such an easy target.

"Phew - it scares me when those guys are around," said an Alpha Company marine as the man in charge of the EOD security left. Then the EOD team got to work, hoisting a small robot - not unlike NASA's Mars Rover - out of the back of a custom-built Humvee.

One marine set up the remote monitor on the hood of the Humvee, which displayed the view from one of four cameras on the robot, while others made an explosive charge and separated the detonation device for the robot to carry to the IED for a controlled explosion.

EOD teams in this area south of Baghdad - a key route for insurgents to shift explosives, cash, and people from their strongholds of Fallujah and Ramadi, west of here, to the capital - have been increasingly busy. And they say that insurgents have become increasingly clever with their IEDs.

A recent innovation is "elevated" IEDs like the one hidden in the cab of the oil tanker. One of the EOD experts told of an earlier attack with one that hit a Humvee, penetrating its armor and detonating a missile inside, which in turn detonated another missile.

Then there was what the EOD experts describe as the "IED nest" that they discovered just a week ago on this same road. It consisted of three explosive charges within 60 yards of each other.

The first was designed to take out a single vehicle. The second would have been used to strike the emergency-rescue crew. The third and largest would have been detonated to hit the Quick Reaction Force that would have responded to the first two attacks.

"It shows someone was thinking it through," said the veteran marine gunnery sergeant who ran the EOD operation and gave his name only as Mike. "It was something I would do."

The robot rolled toward its target and the chem-light left by the marine who first saw the IED. The robot's camera first showed it passing two other burned oil tankers, then putting its own explosive charge nearby while it examined the IED.

The detonation cord, plucked from the sand one foot at a time by the robot's arm, eventually threaded its way through a hole and into the cab. The robot pulled the wire, one segment at a time, until it held fast.

"Prepare yourself for a big bang," said one EOD specialist, looking at the monitor, then at the robot light just 50 yards away, and noting that they were rather too close.

The bang didn't come, so the robot retrieved the explosive charge it had left nearby, and gingerly placed it on the tangle of detonation cord. The robot was withdrawn, loaded into the Humvee, and then all US vehicles were ordered back several hundred yards. "We have no idea how big it's going to be, so brace yourselves!" shouted Mike, as he readied to set off the charge. "Three, two, one! Fire in the hole!"

The blast erupted with a fireball, followed by a blast wave and a hail of shrapnel. Nicholson leaned over a journalist hunkering behind a Humvee, adding protection with his own armored vest.

Then came one huge piece of fragment, hurtling so fast and hot through the air that it sounded like a revving car.

"That robot is priceless," said Nicholson. "It saved 31 bodies."