PORTLAND – The explosion that killed two members of a Maine-based National Guard battalion has shaken up Mainers whose relatives and friends are serving with the unit.

Gone is the illusion that the 133rd Engineer Battalion of the Maine Army National Guard is in a relatively safe spot at Forward Operating Base Marez in Mosul, protected from the fights raging in battle zones like Fallujah.

A suicide bomber Tuesday set off a deadly blast after infiltrating the tightly guarded U.S. base, which is surrounded by blast walls and barbed wire and watched by U.S. troops who check identifications and search people going in.

Killed were Spc. Thomas Dostie, 20, of Somerville and Sgt. Lynn Poulin Sr., 47, of Freedom. Ten others assigned to the Maine unit were injured.

Poulin, a welder with Alpha Company’s maintenance section, was an advocate of “up-armoring” the 133rd’s fleet of heavy construction and transport vehicles with protective steel plating purchased from local vendors.

Dostie and others had moved into concrete barracks 10 months ago because they thought the thick walls would protect them.

But their deaths came not by a roadside bomb or ambush, or by a mortar or missile raining down from above. Instead, it came by a suicide bomber who wore an Iraqi uniform when he set off the blast as soldiers gathered for lunch.

The attack changed the war for Arlene LeBlanc, whose son, Staff Sgt. Andre LeBlanc, is serving near Mosul as an engineer in the 133rd.

“It’s more difficult now,” she said. “It happened once. It could happen again. That’s what’s so hard about it. You never know when you’re going to get blown up.”

Jessie Farrington of Gray said her husband, Sgt. Adam Farrington, had told her the camp came under mortar attacks daily, but the attacks were so off target that they weren’t much of a threat. She and her husband never talked about the possibility of insurgents sneaking into the camp and exploding a bomb.

“That’s an evil we haven’t even considered,” she said.

The battalion’s 500 members have been stationed in Mosul since February and are rebuilding the region’s roads and buildings. Before Tuesday, the 133rd’s only fatality was Spc. Christopher Gelineau of Portland, who was killed last April by a roadside bomb.

While Tuesday’s explosion may have brought the reality of war home to many Mainers, many wives have long understood that their husbands are risking their lives every day, said Tammy LeBlanc, the wife of Staff Sgt. Andre LeBlanc.

“People try to be empathetic, but they don’t understand,” she said. “They say, ‘They’re just building roads and schools, aren’t they?’ But they are doing it while dodging mortars. They have guns. Try doing your work while being shot at. For me, I have always known it has become risky.”

She said the 133rd has served in Iraq long enough, and many families can no longer tolerate the level of anxiety they are experiencing every day.

In Iraq, the soldiers were dealing as best they could with the tragedy.

Sgt. Bruce Miller, a mental health specialist at Forward Operating Base Marez, said his appointment book was full at his Combat Stress Control office. The soldiers, he said, are just beginning to embark on a painful, five-step grieving process.

The first step is denial: “We’re still seeing a lot of that around here,” he said.

Another part of the grieving process in which survivors wonder how, if only they had done something different, fate might have been altered, is called bargaining.

Another emotion is anger, and there was plenty of that. After darkness fell on Marez on Thursday, a firefight between U.S. forces and Iraqi insurgents erupted outside the base. Members of the 133rd gathered outside their barracks and cheered with a vengeance.

“How does that feel?” hollered one voice in the darkness.

Another emotion is depression, which is being felt by many soldiers.

Miller said it will take time for soldiers all over this base to negotiate their way to the final stage of the grieving process: acceptance.

“There’s not a set time limit,” Miller said. “I mean, this could happen from days to months – especially for people who saw what happened and for others who know the people who have passed on.”