Tikrit, Iraq ? Sgt. 1st Class Dale Toomey slipped his iPod buds under his radio headset and cautioned the rookie driver and gunner about potholes, parked cars and pedestrians as the Humvee convoy entered Tikrit.

“Keep an eye on this guy walking on the left,” Toomey, of Gastonia, N.C., barked up to the 18-year-old gunner. “Keep moving left and right, up and down. Don’t be a silhouette.”

As a veteran of the 505th Engineering Battalion, Toomey, 37, and fellow National Guard members from the greater Charlotte, N.C., area were showing their replacements on Saturday what it’s like to drive the insurgent-infested, Tikrit-to-Baghdad highway.

Since U.S. forces have massed in the capital to suppress sectarian violence in recent weeks, insurgent bombings have increased to the west in the Anbar province and to the north, closer to Tikrit.

Toomey, seated in the fourth of the five-vehicle caravan, set his iPod to Tim McGraw. Then, at 10:03 a.m. Iraq time, BOOM!

An explosive hidden in the median rocked the Humvee, the fourth in the five-vehicle caravan. The fifth and last vehicle bore the brunt of the blast.

“IED! IED! IED!” Toomey shouted over the radio. An improvised explosive device had gone off.

Toomey, 37, grabbed a handful of gunner Richard Malloy’s trousers and yanked him to the floor. The young soldier pressed his hands against his Kevlar helmet and buried his head between his knees. Off in the distance, the thump, thump, thump of a firefight between U.S. forces and insurgents heightened the chaos.

“We’ve got one, maybe two flat tires!” the fifth driver, Staff Sgt. Don Chandler, 38, of Silver Grove, Ky., called out. “We’re still moving.”

Iraqi soldiers stand guard at a checkpoint Saturday at the entrance to Baghdad, Iraq. Iraqi Shiite Prime Minister Nouri al-Maliki appealed Saturday for Iraqis to bridge communal animosities by joining his national reconciliation plan.

The fifth Humvee took the fourth spot, as the convoy communicated the extent of the damage. As it passed Toomey, he noted that only the right front tire was damaged. All vehicles kept rolling. A small roadside base was about a mile away.

“It can ride on the rim if it has to,” Toomey said nonchalantly, quickly turning his attention to Malloy, who had returned topside to man his M-249 SAW belt-fed machine gun. “Sorry I jerked your pants down.”

Potholes in Iraq can be deadly. They make ideal hiding places for improvised explosive devices. IEDs are responsible for 969 of the 2,682 U.S. deaths in Iraq here over the last 3 1/2 years, according to Iraq Coalition Casualty Count, a Web site that tracks military fatalities.

Of some 2,000 convoys the 505th has run in its year in Iraq, less than 3 percent have hit IEDs, according to Capt. Kyle Meisner. The numbers look comforting on paper. Inside a Humvee, even an armored one bristling with machine guns and assault rifles, IEDs take on reaper-like meaning.

At the roadside base, the 22 soldiers dismounted and gathered around the damaged Humvee. Many quickly lit cigarettes. Some of those who didn’t smoke stuffed Copenhagen chewing tobacco between their cheek and gum.

One soldier wept.

Each Humvee had at least one member of the 505th along Saturday. All had experienced an IED while on tour in Iraq.

Less than two hours after the attack, the convoy was ready to roll again.

Those in charge decided to continue with the mission, rather than return to base. The convoy would press south to Samarra, have lunch at a base, practice closing a road and checking a bridge, then return to Camp Speicher, just outside Tikrit, Saddam Hussein’s hometown.

It has been blessed so far. The 505th has not suffered a fatality.

“I hate to say it, but what happened today was a good thing,” Toomey told a reporter after the mission. “It was a wake-up call. It’s for real.”