"After a while, it got a little frustrating," said Greer, who is back in the United States with the 101st. The trucks have "come a million miles since then."

With hundreds of U.S. soldiers wounded or killed in Iraq by these explosives, the military has been spending millions to develop better weapons and vehicles, with a focus on the Humvee. Its mobility and adaptability has made it a favorite among commanders in their fight against insurgents.

The result has been better armor, more powerful weapons and high-tech jammers to counter these explosives that are remotely controlled. Soldiers and Army officials say these upgrades have been valuable because they've already helped save some lives.

"There are some things you can't do anything about," said Greer. "But soldiers aren't looking for 100 percent solutions. We're looking for 60, 70, 80 percent."

Iraqi insurgents sometimes encase powerful 152 mm artillery shells in concrete. These blocks would be placed on the side of the road, covered with debris and detonated by remote control as troops or vehicles passed.

Greer, who participated in a trade show where some of the new armor and weapons were on display, rolled his eyes while trying to describe the explosive force of the 152 mm shell. He said concrete chunks and razor-sharp metal shards would slice through the standard Humvee, which has no armor, killing and maiming its occupants.

It was clear that the Humvee needed beefing up, he said, and the Army rushed to find answers.

By the summer of 2003, the military began sending two-door and four-door armored Humvee kits to Iraq, which add considerable weight to the vehicle but provide better protection for troops inside.

"You give up speed for survivability," said Maj. James Riddick, 35, of the Army's Tank and Automotive Research and Development Command in Warren, Mich.

The Army also pushed for production of the so-called up-armored Humvee, which weighs more than 12,000 pounds, or more than twice the weight of the standard vehicle. It requires a more powerful engine and suspension system, but the additional armor does a better job of protecting soldiers if an explosive blasts their vehicle.

A new weapon system being developed for the Humvee also could help avoid casualties from ambushes, according to Lt. Col. Kevin Stoddard. He is helping to develop the Common Remotely Operated Weapon System, or CROWS, which will help soldiers spot the enemy before running into trouble.

The system is computer controlled and allows a gunner within the relative safety of the Humvee to see an enemy target on his computer screen — day or night — and determine the exact location and fire an automatic weapon precisely.

Sgt. 1st Class Sam Cottrell, 38, of Fort Leonard Wood, Mo., and a member of the system's testing program, said the turret gunner is extremely vulnerable to attacks from the improvised explosive devices.

"For each one of these (CROWS), there is a soldier not exposed to danger," he said. "If they're not exposed, they tend to survive IED attacks."

Army Maj. Frank Lozano, 33, who is based at Picatinny Arsenal, N.J., said National Guard military police units have successfully used the system in combat. Military police units were selected because they often provide security for convoys and surveillance of convoy routes.

But while CROWS appears to be a powerful weapon, its ability to help soldiers conduct surveillance and reconnaissance missions may be its most attractive quality.

"The best way to survive an ambush is to avoid the ambush," Stoddard said.

The system has a laser range finder that pinpoints the exact location of a target. The computer then plots a firing solution so that when the weapon is fired, the first shot is on target. The system saves ammunition and maintains an element of surprise against the enemy, soldiers said.