Just last week, the New York Times reported that President Bush's top intelligence advisors told him in July that Iraq's near term future is shaky and could descend into civil war.
As Correspondent Scott Pelley reports, you'll hear the same thing from Iraq's national security adviser, who says American troops are the only thing holding Iraq together.
What does the second war mean for U.S. troops? Now, they're finding that combat is close, sometimes hand to hand.
U.S. troops - 138 Americans - died to topple Saddam. Since then, nearly 900 have died in a war with goals that are not as clear.
Pelley visited a battlefield where soldiers were killed in some of the most violent combat of recent weeks. It's a place known as the Valley of Peace, a 1,000 year old cemetery of five square miles outside the holy city of Najaf. Muslims come here to be buried next to the founder of Shia Islam.
For believers, this is heaven's gate. But for U.S. Marines, it was a battle from hell.
"The majority of the fighting took place about 100 meters down the road, and as you can see, they started coming out of the crypts. It's like a video game. He pops up, fires a couple of shots, pops back down. You see him for a second, maybe two," says Marine 1st Lt. Lamar Breshears, of the 1st battalion, 4th Marine regiment.
He fought in the invasion that freed the oppressed Shia Muslims who are centered in Najaf. He never expected to return on a second tour to fight the people he liberated.
"They had small arms, AK47s, light machine guns, rocket-propelled grenades," says Breshears. "The two faces I saw, you know, mid-20s, young males fighting for what they believe in."
The battle in the cemetery in August was one of the bloodiest examples of what the war is about today. American GIs provide firepower and protection for a new Iraqi government with many enemies. What would happen if American troops left tomorrow?
"This is a recipe for civil war. There's no doubt about it," says Mowaffak al-Rubaie, the interim government's national security adviser and a chief negotiator with the rebels in Najaf. "A messy, really dirty civil war, because it will be on religious grounds, on sectarian grounds, on ethnic ground, on all sorts of grounds."
Can America achieve success in Iraq, or is the idea of success out of American hands at this point?
"I have no shadow of doubt in my mind that Iraq, in the next 5 to 10 years, is going to turn around," says al-Rubaie. "And it's going to be the beacon of democracy. This is going to be an example of prosperity, stability and really an example for the whole region... I'm talking about the whole experiment of liberating Iraq."
In that experiment, there are explosive elements – like the Mahdi Army, a few thousand strong. No one's sure how many, led by a young, junior cleric named Muqtada al-Sadr. His goal is to make Iraq an Islamic state, not unlike Iran.
Last month, al-Sadr's followers essentially hijacked Najaf. Al-Sadr seized the Imam Ali Shrine, among the holiest sites on earth to Iraq's Shia majority. Al-Sadr urged his followers to fight the Americans to the death – and a lot of them did just that.
The Marines came under fire from hundreds of militiamen hidden in the cemetery. Breshears warned his men the combat would be different now.
"I told them this is what you've been preparing for your entire Marine Corps career," says Breshears. "The war was easy. If you look at the terrain out there you know what we're getting into, let's go get 'em."
Video from an Arab television channel shows the intensity of the fight. Americans didn't see much of this, because there were no TV cameras with the Marines down below in the mausoleum maze. But there was a still photographer, Lucian Read, who moved through the cemetery with the Marines, capturing the battle up close – sometimes at the side of Breshears.
"When you have that many people, that many rifles, that many machine guns, you have grenades exploding, rocket-propelled grenades exploding, rockets being fired, it's deafening, it's a dull roar," says Breshears.
Staff Sgt. Ian Bonnell is in Breshears' platoon. "I didn't want to go in there. The first day that we showed up, we're on a wall. And we're taking all the fire in there. And I just kept thinking to myself, 'We're gonna have to go in there,'" he says. "It played out pretty much how I expected it... Close-in fighting, getting up close and personal with people."
In some cases, says Breshears, that means 5 feet, and "in some cases 20 feet, close enough where you could throw hand grenades at each other. You could smell them. You could smell their living spaces. That sort of thing. So it was very close contact."
The fight in Najaf became one of the fiercest urban battles that U.S. forces have seen in the entire campaign.
As the companies of Marines were moving through the cemetery, there were other Marines who were addressing the buildings in the old city. One Marine commander said that he had 150 Marines concentrated in a very small area entering the buildings.
This was the kind of the close order combat that most everyone was concerned would happen in Baghdad, but never really materialized until in Najaf. One Marine officer said his men were fighting hand to hand, and when they couldn't reach their side arms, they used knives for fighting instead.
The Iraqi's best weapons were mortars which rained down, wounding Marines in the cemetery. Staff Sgt. Robert Willis lost a lieutenant, a radio operator, and a medic in the same mortar blast. When his lieutenant was wounded, Willis called the Marines to a huddle, took over his platoon and pressed the attack as another mortar came down.
"It landed at our feet and had hit my corpsman, my second corpsman, and hit my radio operator and hit one of my squad leaders, about 25 meters behind it," says Willis.
"Down the line, you could hear everyone yelling 'incoming,' and at one point, I remember looking over and the chaplain that was with us," says Bonnell. "He was walking up and down the lines and it wasn't even fazing him. A round would go off and blow up and he'd turn around and look and start walking that way to make sure everyone was OK."
That chaplain, Father Paul Shaughnessy, blessed the Marines as they fought. Photographer Lucian Read's pictures tell the battle's small stories. Soldiers catching a moment's rest. Calling for help after finding the body of a fallen American. Carrying the wounded to safety.
And in another picture, Sgt. Yadir Reynoso is helping to treat a wounded Marine as the medics move in. Hours later, Reynoso was killed by enemy fire. He was one of nine Americans to die in the three-week battle – about 100 were wounded.
As for the enemy, no one knows how many Mahdi Army soldiers were killed — but estimates are in the hundreds. In the ceasefire, al-Sadr agreed to give up the Holy Mosque, but he and his fighters were allowed to walk away with their weapons to fight another day.
"Removing Saddam liberated the Shia. And now, the U.S. is fighting the Shia. How did we lose them?" asks Pelley.
"America is not fighting the Shia now. And the Shia are not fighting America now," says al-Rubaie. "It's a small group of people who has perceived the liberation wrongly for their own political gain and for their own personal ambition."
Attacks continue through much of Iraq, launched by those al-Rubaie says have "perceived the liberation wrongly."
Last week, there were close to 20 terrorist bombings. In downtown Baghdad, one blast killed nearly 50 people outside a police station. To the west, the Marines won't even enter the city of Fallujah in Al-Anbar province. It's a town of a quarter of a million people in the hands of the rebels. The Americans tried to install a mayor in Fallujah, but the office isn't in Fallujah and the mayors are not in the office.
"I have to admit that this province is a troubled province," says al-Rubaie. "And potentially, it can be a troubling one."
But peace, prosperity and democracy in Iraq can't be achieved without bringing Al-Anbar province along.
"Absolutely. Al-Anbar is an integral part of Iraq," says al-Rubaie. "And if we start the economy there, if we give them some jobs, if we get the tribal sheiks together, and try to sort out their differences, I think we will be able to abort a potential problem there."
In Al-Anbar, the Americans are trying to buy what they can't take by force. Just outside Fallujah, they were pulling out fresh bricks of $100,000 dollars each, handing them over to this man to build barracks for the Iraqi army.
The security problem, however, is part of every Iraqi's life. On the outskirts of Baghdad, there is an assembly line running long into the hot afternoon. These men are paid $5 a day, and they're glad to get it. Orders are rolling in from the Americans and the Iraqi interim government.
They just can't build enough of these concrete barriers. There are walls in Iraq that are now 16 feet high and miles long — sealing off American bases and Iraqi government offices. The ramparts run 16 feet high and miles long in some places, separating America's hope for Iraq from its current reality.
Back in Najaf, some of the Marines are frustrated after the battle. Some feel they paid too great a price to let al-Sadr go. Some complain they've become a tool of Iraqi politics. Others say Najaf is uneasy, but at least it's no longer under siege. And as Willis points out, plenty of Iraqis were glad to see al-Sadr and his fighters go.
"I can say the best thing right now is how the people reacted when we left, letting us know 'Hey, thanks,'" says Willis.
After 16 months, the battle is different now. Instead of weapons of mass destruction, they're finding combat close and personal. Many Americans, fighting in places like the graveyard, have buried their early hopes of what a liberated Iraq would be.