WASHINGTON – In a horrifying way, the explosion that tore apart the giant tent that served as a dining hall at an American military base near Mosul, Iraq, was neither unusual nor unexpected.

Soldiers at Forward Operating Base Marez south of Mosul already had described in e-mails to their families their unease about the safety of the dining hall – a long, high tent pitched atop a concrete pad – and the ability of Iraqi insurgents to target the base.

Easter Sunday was particularly bad, as Adam Szafarn, a 23-year-old specialist with the Maine National Guard, told his family.

“There was just round after round after round,” his mother, Sheila Szafarn, said Tuesday in a telephone interview from South Portland, Maine, recalling that her son and other soldiers spent much of that day in concrete bomb shelters. “They couldn’t go anywhere. They were just riding it out.”

Her son e-mailed her after Tuesday’s attack to say he was safe, but his mother remembered earlier messages about the dining tent. “He doesn’t like going to the dining hall, because of the lack of safety,” she said. “It’s a soft building.”

Thanks to a plentiful supply of mortars and rocket-propelled grenades and a lack of U.S. troops to patrol the perimeter of forward bases, Iraqi insurgents are able to strike with relative ease.

Mortars rained down on the mess hall more than 30 times this year, according to a report by the Richmond Times Dispatch, which has a reporter embedded with soldiers there. One round killed a soldier last summer as she scrambled for cover, the paper’s Web site said.

Just hours before the mess hall blast, a soldier from a Virginia National Guard unit was awarded a Purple Heart for wounds she suffered in a mortar attack in October targeting another part of the base.

The situation at the Mosul base echoes the daily routine of soldiers at Forward Operating Base Anaconda – dubbed “Mortaritaville” – farther south outside Balad. At least a half-dozen soldiers and contractors have been killed and nearly 100 wounded there since April. There have been about two attacks a day since July.

Retired Army Lt. Gen. John Riggs, a Vietnam War veteran who shared responsibility for modernizing the Army before stepping down earlier this year, said such attacks would not occur if more troops were on the ground to provide security for U.S. operating bases and supply hubs.

An Army officer with experience in Iraq and now based at the Pentagon complained Tuesday about the decrease in the number of U.S. troops this year in the Mosul area.

In February, the 101st Air Assault Division was responsible for providing security in northern Iraq with about 17,000 soldiers. The division was replaced by a 4,000-soldier brigade from Fort Lewis, Wash., and 4,500 National Guard and Reserve soldiers.

It’s unclear whether more soldiers will be dispatched to help protect the bases.

Brig. Gen. Oscar B. Hilman, commander of the 81st Brigade Combat Team, a National Guard unit from Washington state that operates Forward Operating Base Anaconda, twice this year requested 500 to 700 more soldiers to beef up security outside the base. But he said in October that his requests for more troops had been denied.

Ed Heasley, curator of the U.S. Army Ordnance Museum at Aberdeen Proving Ground, said the attack on the Mosul base could have been carried out by an RPG-7, a shoulder-fired rocket-propelled grenade that is cheap, reliable and easy to use. It has become one of the weapons of choice for insurgents.

While soldiers were caring for the dead and wounded Tuesday at Marez, workers down a dusty road at the base were constructing a new steel and concrete mess hall for the soldiers.