Pelley and a 60 Minutes crew spent two weeks with the Marines in November.
The battalion, known as 2/5 Marines, is on its second tour in Iraq. For these men, the resistance has turned out to be far deadlier than the invasion itself.
60 Minutes first aired the story in January as the Marines were "under fire" in Anbar province, the heart of the resistance.
Every morning, the colors rise outside Whiskey Company, 2/5 Marines. To the flag, the Marines chain the dog tags of the men who died under the Stars and Stripes.
In the war to topple Saddam, the battalion lost one man. In the war on the insurgency, it's lost 14, most of them from Whiskey Company.
Cpl. Jake McCloskey won a purple heart for wounds suffered in September.
He says his second tour has been a lot harder than the first. "It's an enemy I can't identify right away. Last time ,uniforms made it a lot easier. These guys hide, they hide with the regular populous and it's very difficult to find them."
With 60 Minutes cameras present, a patrol in Ramadi was hit with a rocket-propelled grenade, seemingly from nowhere.
Pfc. Josh Johnson was badly wounded.
Second Lt. John McKinley, the patrol's commander, says, "Right now he's unconscious. Sounds like it came from the north, sir. From over our head. Roger, it sounded like it came from over our heads, don't know if it was a mortar or an RPG. Did it come from the north? Hey, how is he, doc? What have we got. Hey, let's not lose our minds here. Let's see this, roger, he's bleeding pretty bad out of his leg right now. We definitely need to get him out of here. He's definitely an urgent right now."
They did get him out. Johnson, with shrapnel in both legs, was medevaced to a combat hospital. He's home now, in the United States, making a full recovery, one of about 150 men wounded in the battalion since September. His comrades never found the man with the RPG.
"It's three dimensional. Every direction up, down, left, right, below you," says McCloskey. "I mean there's always a possibility that somebody could pop out somewhere, there's an IED [roadside bomb]. Sometimes you can't see them. A lot of times, you can't see them so you've got to be constantly looking for something that maybe the day before that wasn't there." He figures you can tell if something isn't right two times in 10.
Whiskey Company corporals Jack Evers and Joseph Terwilliger said if the Marines don't know what's about to happen, the people in town usually do.
"Most times before it happens, the general populous is gone. They'll go inside and they lock up their shops and they leave. And nine times out of 10, the people left out there are the insurgents or whoever it is attacking us, and it's us versus them at that time," says Terwilliger.
"Just drive by a group of locals and then 10 minutes later you can drive back by and the same guy is walking by you, can be pointing an AK [automatic rifle] at you, or shooting an RPG, or setting an IED out alongside the road. So they're guerrillas out here."