He taught his young charge all the details of the military funeral, how to carry a coffin and fold a flag. Perhaps most of all, Maryland National Guard Sgt. Derrick Hayes taught Spec. Bernard L. Ceo the importance of poise.

"I told him to try to concentrate on the performance, because it's emotional, and you can get sidetracked," Hayes said. "You have to stay focused and look good for the family and maintain your military bearing."

Now it is Hayes and the other members of the honor guard who are trying to keep emotions in check as they wait to see whether they will be called to serve at the funerals of three fellow soldiers, including Ceo, who were killed in Iraq last week.

In addition to Ceo, 23, of Baltimore, Sgt. Brian R. Conner, 36, of Baltimore and Spec. Samuel M. Boswell, 20, of Fulton died Friday after an 18-wheel tractor-trailer accidentally slammed into the back of their ammunition-laden Humvee during a convoy in Al Taji, according to the Defense Department. They were members of the 243rd Engineer Company, which has been in Iraq since August.

They were the first Maryland National Guard soldiers killed abroad in the line of duty since World War II, another grim milestone in a war in which almost 2,000 service members have died.

Since the Sept. 11, 2001, attacks, about 4,600 of the Maryland Guard's "citizen soldiers," who normally serve one weekend a month and two weeks a year, have been called to active duty. Hundreds more have been mobilized in recent years for domestic emergencies such as snowstorms and hurricanes.

Some have patrolled airports and secured domestic bases. Others have been sent to Afghanistan and Iraq, where they have fought alongside their active-duty counterparts.

Almost 100 service members with ties to the Washington area have died in the Iraq war, and five members of the Virginia National Guard have been killed in Iraq or Afghanistan.

There are 607 Maryland National Guard soldiers serving in Iraq, according to Maj. Charles Kohler, a Guard spokesman. Several Maryland guardsmen have been injured in the war, he said, but until Friday, none had died.

"You're never really prepared for it," Kohler said. "It is something that as a soldier you know can happen, but it's always a shock when it does."

As the death toll climbed, Maryland National Guard officials had counted their blessings that none of their soldiers came home in coffins. Yet they trained with the sense of urgency that comes with knowing that the call to war could be issued at any moment, Kohler said. Veterans who had returned from Iraq shared their war stories with those who had not yet been deployed. Even the chaplains began training to survive combat situations.

But for many of the soldiers, the deaths of their comrades have made the war hit home.

"These three deaths are a reminder that this can happen to any of us," said Col. William Sean Lee, the Maryland National Guard's senior chaplain. "You can't help but feel the loss personally. It's the nature of what we do."

As the news spread, Hayes said, soldiers took it hard.

"Everybody is still pretty much in shock," he said. "It's hard to believe still."

Conner was a lieutenant with the Baltimore fire department and a single father of three, said Kevin Cartwright, a spokesman for the department, which is preparing a memorial service.

Boswell graduated in 2003 from River Hill High School in Howard County and was a country boy in style and at heart.

"He was given to cowboy boots and big hats," said Jack Dewell, who worked with Boswell at a hardware store in Clarksville.

Ceo had volunteered for the honor guard shortly before he deployed to Iraq. He was still learning the rituals of a full military honors funeral when he left, Hayes said. "He said he thought it was an honorable job," Hayes said.

Staff writer Michael Alison Chandler contributed to this report.