IED's come in all shapes, sizes, and varieties – from sophisticated plastic explosive bombs to old mortar shells wired together and attached to a detonator.

They can be packed in cars or trucks, or placed at the sides of roads in plastic bags, piles of trash, or under rocks. They can also be buried and explode like land-mines.

No wonder, then, the U.S. military has fielded a number of high-tech and expensive countermeasures to the devices. But it's still the job of anxious men to seek out and destroy them.

"Mentally it doesn't bother me a lot, but my awareness certainly goes up," says Marine Pvt. Anthony "Chase" Watson. "But if you're afraid to do the job you shouldn't be here," he adds.

Watson, 23, has a particularly dangerous role in the 1st Combat Engineer Battalion, based at the U.S. military base at al-Asad, approximately 110 miles west of Baghdad.

As a member of a route clearance team Watson, by choice, drives a vehicle called a Husky, which looks like an outsized, armor-plated dune buggy. His job is to drive slowly along the sides of roads to locate and mark hidden mines using highly sensitive electronic sensors and his own sight. Other team members follow up in a special mine resistant, ambush protected vehicle, or MRAP, on which is mounted a long hydraulic arm that is used to dig up the IED's and snip their wires or destroy their detonators.

Watson marks a mine by electronically pinpointing the center of the object and then spraying it with ink using a special tool fixed to the front of his vehicle.

If his Husky passes a hidden mine, a trailer it sometimes pulls behind may roll over the IED setting it off. The vehicle is fortified front and rear to absorb most mine blasts.

Watson, in a deadpan voice, says he's so far avoided that experience. A friend didn't get off so easily, he says. His Husky exploded a large mine, but neither he nor his vehicle sustained anything serious. "These hulls are designed to withstand a blast," Watson says.

Other mine-resistant vehicles used by the battalion include the Cougar and Buffalo, which look like large boxes on wheels. The four-wheeled version of the Cougar is more than 19 feet long and has a curb weight of 32,000 pounds. The Buffalo is more than six feet longer and weighs in at more than 43,000 pounds. The Cougar carries the engineering crew, while the Buffalo carries team members and a de-mining arm. Each carries six people or more people.

"We've gotten a good reputation, I guess," says Lt. Trevor Holmes. People keep asking for us to do stuff for them, so we keep pretty busy."

Almost daily, elements of the 1st CEB work the major routes that cross AO-Denver, an area in western Anbar province the size of South Carolina. Their main priority is to clear roads reserved for military vehicles, although they'll also clear roads used by civilians.

A 12-hour de-mining mission is not unusual.

"You're all pumped up the first eight hours, but you can't wait for the last four to end," Watson, from Yemassee, South Carolina, says.

A recent short mission, a little beyond al-Assad, hub of U.S. military operations in western Anbar province, sees Watson and his comrades slowly clearing a main highway.

Watson is at the front right-hand side of the road, his Husky slightly on the tarmac and mostly on the verge. A second Husky is doing the same on the road's left side. Following down the middle of the highway are the Cougars, a Buffalo, and a truck to cart off any damaged or destroyed vehicles they come across.

The drill is always the same. Before departing they make note of the base maps and routes to be searched. They repeat operating procedures: the actions that each vehicle will take if an IED is found or if a vehicle strikes a mine, or if anyone is injured.

The desert military road this day is almost without traffic or incident, so the Marine engineers riding as passengers inside the air-conditioned monsters amuse themselves with tall tales and statistical trivia, such as that it takes beam of sunlight eight minutes to reach the earth, and that a person will spend an average of four hours of his life tying his shoelaces.

Watson doesn't allow himself to be distracted, though, as the Husky is a one-man show.

Several times the convoy stops abruptly and tensions rise. A mine-detection instrument on the console of one of the Huskies has given off a warning ping or they will stop to check on something suspicious, such as freshly turned earth. Nothing dangerous is found and they move on.

In villages and towns the Marines grow quiet as they scan the streets for any unusual behavior or situations - people moving away too quickly, or a vehicle that arouses their suspicion, or a street that's deserted when it shouldn't normally be.

The large vehicles have difficulty maneuvering the narrow roadways of settlements. They make three-point turns, which leave them vulnerable to attack. But despite being extra cautious in populated areas, they sound out two-honk greetings to people, wave, and toss candy to children.

Then it's back out on the highway, and to the tedious, but essential business of de-mining.

Military authorities in Baghdad have reported a big drop in IED incidents in Anbar province in recent months. But to Watson and his comrades, the overall IED count is just an abstract - a single IED is one too many.