By Matt Haan
Producer, The Insurgency
As a US tank comes into view on a street in Ramadi, west of Baghdad, three fighters in civilian clothes and headscarves aim their weapons and wait. They claim to be part of al-Qaeda in Iraq.
"This is a message to America," one insurgent says to the camera.
"Look at your might and power, yet you are unable to walk the streets of Ramadi, which belongs to the mujahideen."
Al-Qaeda insurgents see themselves as challenging US power
He turns back to the tank, which has paused a few blocks away. "I swear by almighty God we will destroy them," the insurgent says.
We received this footage while making a documentary about the Sunni insurgency fighting the Coalition Forces in Iraq.
We had asked local fixers and stringers in Baghdad if they would be prepared to take a camera and a list of prepared questions into the heart of the Sunni Triangle to speak directly with insurgents. Few accepted such a dangerous task.
Of those that did, one person got past the roadblocks with the film of al-Qaeda in Ramadi.
New generation of fighters
Cases of US heavy handedness or the abuse in Abu Ghraib have provided fertile ground for the insurgents to recruit from.
"A number of the insurgents keep saying to me that this is what I was trained for," journalist Michael Ware explained to us.
"They say the next generation is going to be worse than we've ever been. And it's in this way that it's al-Qaeda that are one of the main beneficiaries of this war.
"The Bush administration is the midwife to the next generation of al-Qaeda. And that's a generation that is principally being shaped by Zarqawi," Mr Ware said.
The normal methods of making a documentary about the evolution of the Sunni insurgency are not possible in Iraq.
Our contact with the insurgency came in two other ways.
Firstly, through two journalists - Michael Ware, who has had contact with members of the insurgency from the very beginning; and Ghaith Abdul-Ahad, who has travelled throughout the Middle East to understand more about the foreign fighters coming to fight in this war.
And secondly we embedded with US and Iraqi forces. We filmed the raids they were making to counter the insurgency.
The officers we spoke to were exceptionally candid about the realities of the situation and the problems resulting from past mistakes. Something we were not expecting.
But what did we learn?
That the disbanding of the Iraqi army and the Baath Party had been a monumental mistake.
At the end of the war, there was a moment when a policy of inclusion might not have pushed people into opposition.
That the insurgency consists of three main groups - the foreign element led in part by Abu Musab al-Zarqawi; the nationalist element of former Iraqi soldiers and Baathists; and a middle ground of Iraqi Islamic nationalists.
That the insurgency has developed into an organised, structured force, leading an increasingly effective campaign.
"Falluja was a moment of transformation for the resistance. It became a secure area for the resistance to work," Abu Mohammed, a representative of the national resistance, told us.
A marriage of convenience between these groups took root during the first battle of Falluja in April 2004 when US troops could not take back the city.
We also leant that post-Falluja, this co-ordinated insurgency spread across Iraq.
Some cities fell completely under the control of the insurgents.
Reign of terror
We travelled to Talafar, in the north of Iraq near the Syrian border, and spoke to residents who had lived through a horrific reign of terror when al-Qaeda ran the city.
"The terrorists shot my brother with two bullets in his stomach - they cut open his stomach and put explosives inside," said one man.
"My father wanted to go and pick him up. They blew up my father, beheaded him and put his head on his corpse."
Foreign fighters, estimated at only 15% of the insurgency, have had an enormous impact.
They have provided men, money and weapons to trained officers from the former Iraqi army.
And they provided an ideology that has struck a chord with some disenfranchised Iraqis.
An ideology witnessed by journalist Ghaith Abdul-Ahad in Falluja before the Americans retook the city in November 2004.
"A Yemeni fighter would tell me about his pregnant wife, his children and the young daughter that he loves very much. And then you see tears running down his eyes and then he would dismiss this, oh no, no, this is the devil trying to tempt me away from my Jihad by reminding me of my family."
Driving the insurgency
So would Iraq be better off if US and British troops withdrew?
It may remove one motivation for the insurgency.
"The resistance is a natural reaction to any occupation," says Abu Mohammed. "All occupations in history faced a resistance - this occupation is an insult to me and my people.
"Since I'm an officer, the responsibility falls on my shoulders. So I have to finish this occupation."
But above and beyond the motives of the nationalists, there is the "game plan" laid out by Zarqawi in a letter in early 2004.
One of the primary aims was to foment civil war between the Sunnis and Shias. Recent events in Iraq show this agenda is still being vigorously pursued.
An Iraqi officer we spoke to said that if the international coalition were to pull out of Iraq, "You can forget about a country called Iraq. There'd be massacres in the street - Sunnis will kill Shias and Shias will kill Sunnis".
"The Muslim will kill the Christian and the Christian will kill the Muslim. The Arab will kill the Kurd and the Kurd will kill the Arab. It is very, very important that the coalition forces stay in Iraq," the officer told us.
The Insurgency will be broadcast on BBC Two on Sunday, 2 April at 2100 BST