It was the deadliest attack on American troops in nearly four months.
That's because, as CBS News correspondent David Martin reports, the Marines didn't encounter just one buried artillery shell. They met four, strapped together and connected to a booby-trap in-ground plate that triggered the massive and deadly explosion when a soldier likely stepped on it.
This sort of piecemeal trap of a weapon, called an "improvised explosion device," is the single-biggest killer of American troops. And it seems to be getting more popular among insurgents as suicide bombers become more difficult to recruit.
Another trend seems to have been at work in the chain of events leading up to these Marines' deaths. As Iraqis become more comfortable with the presence of U.S. troops and Iraqi soldiers, citizens are becoming intelligence providers.
"One trend that is really extremely encouraging is the number of tips that are being provided to Iraqi armed forces and coalition forces by Iraqi citizens," said Gen. Peter Pace, chairman of the Joint Chiefs of Staff.
Sometimes the tips are reliable, but sometimes they are deadly.
As Martin reports, the members of Regimental Combat Team 8 of the 2nd Marine Division near Fallujah were on foot patrol responding to a tip — that very well could have been a set up.
And with bigger, more sophisticated bombs, the combination can be deadly.
"They're bigger. The IEDs are bigger," one soldier told CBS News last January. Another said: "Yeah, they're finding better ways to hide them and they keep getting bigger and better."
In related developments:
The military statement said seven of the wounded later returned to duty and that the rest of the team was conducting "counterinsurgency operations throughout Fallujah and the surrounding area" to improve security for the Dec. 15 elections.
Names of the victims were not released pending notification of their families. The statement also did not give the precise location of the attack the single deadliest against U.S. troops in Iraq since 14 Marines were killed Aug. 3 when a bomb destroyed their vehicle near Haditha, 140 miles northwest of Baghdad.
The Bush administration says it's "saddened" to hear of the deadly roadside bombing that killed ten Marines in Iraq.
Press Secretary Scott McClellan says a loss like this represents a "tough day" for the U.S. cause — the kind that President Bush has warned about.
At least 2,121 members of the U.S. military have died since the beginning of the war in 2003, according to an Associated Press count.
The attack came after U.S. commanders reported a drop in suicide and car bombings as a result of increased U.S.-Iraqi operations.
In the month of November, "there have been only 23 suicide attacks — the lowest we've seen in the last seven months," said U.S. Army Maj. Gen. Rick Lynch.
But CBS News correspondent Charlie D'Agata reports that those attacks killed 290 Iraqis, which is double the number from the previous month.
Pentagon officials say the Marines were patrolling on foot near Fallujah yesterday when the bomb went off.
Of the 11 who were wounded, seven have returned to duty, the Marine Corps said. It added that Marines from the same unit continue to conduct counterinsurgency operations throughout Fallujah and surrounding areas.
Regimental Combat Team 8 is a part of the II Marine Expeditionary Force based at Camp Lejeune, N.C. The unit has been among the hardest hit in the war. In the nearly three years since the war began, 147 Marines from II MEF have died in combat, according to 2nd Marine Division spokesman Lt. Barry Edwards.
Regimental Combat Team 8 has been in Iraq since the beginning of February.
Fallujah had been a stronghold of the insurgents until U.S. forces, led by Marines, assaulted the city in November 2004. Since then, the U.S. military and the Iraqi government have been working to rebuild it and limit the return of insurgents.