The young man calls himself Ahmed. He is 23 and he has a degree in chemistry. He knows all about explosives.
Last year, he says coolly, he took 15kg of TNT, packed it into pouches with some nails, and strapped the bomb to his 19-year-old brother's waist.
There was never any doubt that it would go off. Ahmed placed detonators in both his brother's trouser pockets and a third in a shirt pocket, just in case the others failed.
Finally, he slipped wire rings on to his brother's fingers and attached them to a fourth detonator in the palm of his hand. The thinking was that even if his brother were shot, he would clench his fist and the TNT would still explode.
Ahmed had borrowed a drinks stall used by American convoys on the road that winds north from Baghdad past Saddam Hussein's home town of Tikrit. His brother was instructed to grab some bottles of cola in his free hand and head for a group of soldiers taking a break from their journey.
"Go sell them some Pepsi," Ahmed told him gently. "We will meet in heaven, you and I, and that's a promise."
Ahmed says his brother kissed him, turned and walked away without a moment's hesitation. Did he not long to call his brother back, I ask? The question brings tears to his eyes.
"He had a smile on his face," Ahmed replies. "He knew he was crossing to a better place where he would meet his maker as a martyr."
The emotion passes and Ahmed talks with steady self- assurance about his plans to follow his brother's example. He too will take Americans with him when he dies, he says. His ambition is to blast some CIA men to smithereens.
The flat where we met was rented by a handler in Damascus, the Syrian capital, who channels aspiring "martyrs" toinsurgent groups such as Ahmed's.
Our encounter was arranged as part of a four-week investigation into the world's biggest suicide bombing campaign.
More than 1300 bombers are said to have struck on foot or in vehicles since the American-led invasion of Iraq in 2003 - more than all the other suicide bombings of the past 20 years put together.
The number this year promises to be higher than ever. The bombers are estimated to have killed and injured more than 4000 people in the first nine months.
Their targets have ranged from lines of police recruits in and around Baghdad to an entire village near the Syrian border where up to 500 died.
So who are these bombers and why do they do it? How are they organised? And how much impact are they really making on a war that is sucking ever larger numbers of suicidal volunteers from across the Middle East into Iraq's vortex of violence?
We tracked down three bombers in our search for answers. The first interviews of their kind with men passing through Syria on their way to die in Iraq, they confounded expectations.
These were no psychopathic loners from the ghetto but articulate middle-class men in their 20s and early 30s who had come from good homes and gone to university. One was a newly married accountant.
Yet all had reached the chilling conclusion that killing "sinners" would transport them to paradise. None had the slightest inkling that they might be exploited by al-Qa'ida and other battle-hardened groups which will probably use these fresh-faced idealists for no higher purpose than to sustain the most brutal sectarian conflict of our age.
Sipping a Turkish coffee and smoking a hubble-bubble pipe, the middle-aged man waiting for us at a cafe in Damascus 13 days ago could have been any commercial supplier breaking his Ramadan fast after work.
But Abu Ziad's is no ordinary business. He takes eager volunteers, inveigles them into Iraq for a fee and delivers them to insurgents who consign them to a bloody death with clinical efficiency. His network includes the imams who drum up the volunteers and forgers who create new identities for their journey across the border with Iraq.
Then there are the officials he bribes to turn a blind eye, and insurgent groups ranging from the pan-Arab, fundamentalist al-Qa'ida in Iraq to the Iraqi nationalist 1920 Revolution Brigade, started by former members of Saddam's armed forces.
Abu Ziad appears to receive no help from the Syrian authorities, which have been accused by some in the West of aiding the flow of terrorists into Iraq. On the contrary, he seems to live in fear of discovery by Syria's security apparatus.
We left the cafe in a taxi and alighted in a street crowded with late-night shoppers. There we switched to a second car. Only when Abu Ziad was satisfied that we were not being followed did he direct the driver to the flats where we met our first bomber.
We shook hands with Ahmed and sat on sofas, eyeing each other anxiously, while Abu Ziad turned up the sound of a soap opera on television to render our conversation inaudible through the thin walls.
I told Ahmed that he was looking at me with a hard expression on his face. Had I offended him in some way?
"No," he said with a grin. But the smile vanished as quickly as it had come and did not return during our five hours together.
Ahmed is an Iraqi whose small, dark eyes reflect the horrors he has witnessed. He comes from a military family. While he studied for his degree in Baghdad, he served in the Fedayeen, or "Men of Sacrifice", a paramilitary group loyal to Saddam.
When Saddam was toppled in the spring of 2003 Ahmed was outraged. Although he was little more than 18 years old, his father encouraged him to gather together a group of neighbours to resist the occupation in their Sunni area of Baghdad. For their first attack, they rigged up a box of grenades to be detonated as a US troop-carrier passed by. They called their weapon the "fearsome invisible enemy" and used it again and again.
Ahmed's tiny band of followers eventually joined forces with two other insurgent groups and extended their operations beyond the capital, but he was arrested near Tikrit.
It was in prison that Ahmed first heard about suicide bombing. His interest was stoked by clerics whose fiery sermons the Americans obligingly photocopied and distributed without the slightest understanding of their destructive force. Seminars followed on the making of suicide belts, the selection of targets and the timing of attacks.
By the time Ahmed emerged from jail he had not only been radicalised but was armed with deadly new skills. Arrested a second time, he tricked his way to freedom by promising to inform on his fellow insurgents. Instead, he presented them with a proposal to carry out the group's first suicide mission himself.
His men objected, reasoning that, as their "emir", or commander, he was too valuable to be sacrificed. The task should fall to one of their number, they insisted.
Ahmed now made his fateful decision. To show the men that he valued them as much as his own flesh and blood, he chose his brother for the attack.
As the teenager strolled casually into the group of soldiers on the Tikrit road, cola bottles in one hand and detonator in the other, Ahmed heard the Americans asking him what he wanted. This was the predetermined cue for detonation.
Ahmed and his men turned from the scene, climbed into a waiting vehicle and drove off.
He recounted the details to his father, who expressed satisfaction. But his mother was distraught: "One minute she cried at her loss and the next she ululated with joy and pride."
The couple are soon to lose Ahmed, their only remaining son, though he has sisters aged 12 and 9. While Ahmed's girlfriend, a university student in Mosul, knows nothing about his impending suicide mission, his father has said he will be proud if it proves "worthy" - in other words, if he kills the enemy.
The determination to kill Americans was common to the three bombers interviewed for this article, but is highly unlikely to be fulfilled by all of them. Fewer than a quarter of suicide bombers succeed in blowing up coalition forces, who are relatively well shielded behind concrete barriers or the armour plating of their vehicles.
The bombers are much likelier to be deployed against Iraqi Shi'ites - soldiers, police, officials or even civilians. According to academics who have studied the Sunni insurgency, the main aim is not to avenge the destruction inflicted by US forces but to broaden the sectarian divide, perpetuate the cycle of hatred and undermine confidence in the ability of the Shia-led government to restore order.
And so a warm welcome awaits the volunteers streaming into Iraq from other countries to mutilate the Shi'ites. The insurgents embrace men such as Abu Ibrahim, the newly wed accountant, before giving the order to kill and die.
Abu Ibrahim, 28, our second bomber, was due to leave his native Syria last weekend for Iraq. He wanted to complete his mission by the end of Ramadan in the middle of this month. But first, he said, he would have to do something about his bride.
Speaking at his elegant, traditional home in a town we agreed not to identify, Abu Ibrahim, whose family owns two wholesale fruit businesses bringing in $560 a day, explained that he had become engaged two months ago to an educated young woman. "She loves me and I just adore her," he said. "I am crazy about her."
He listed the dowry items he had promised her, as perhaps only an accountant in love would do: gold jewellery to the value of $1400, clothes worth $700, items of furniture for their home and so on. They have undergone an Islamic wedding ceremony but Abu Ibrahim refused to consummate the marriage and intended to divorce her before he left so that she could find another husband, her honour intact.
"She begged me to let her come along so that we could carry out a joint mission," he said proudly. "She told me that would be the best honeymoon, in heaven together."
Instead, he was arranging to make sure that she was financially secure after he had gone. Asked why he had married her when his suicide mission was already planned, he cited Islamic doctrine: he must carry on in life as if he would live for eternity but he must also prepare for his end as if each day were his last.
His radicalisation came in two stages. "I had no Islamic inclinations at the start of the war," he said softly. But when he sat with his parents watching television as the first bombs of the Shock and Awe campaign fell on the country next to his the strength of his reaction took him by surprise.
"I felt a tightening in my chest and a feeling of personal offence and injury, as though every Iraqi woman was my mother, wife or sister, every little boy my young brother and every old man my father," he said. "I spent all night crying in my bed, and in the morning I left the house and applied for a passport."
He had decided to fight in Iraq. His mother gave her blessing, saying she wished for Allah to accept him as a martyr if need be but that she would never forgive him if he became a prisoner.
His father, however, was so opposed he hid Abu Ibrahim's passport. His son stole it back and joined about 400 fellow fighters in the north of the country.
He described with bitterness how he witnessed the defeat of Saddam's forces near Mosul and then found himself detained, just as his mother had feared.
Now came the second part of his transformation into a jihadi. In prison he met Sunni clerics from Saudi Arabia and other countries. These were followers of the Wahabi tradition of Islam which casts Shia Muslims as heretics. They were also supporters of al-Qa'ida in Iraq. They idolised Osama bin Laden and lauded the September 11 attacks on America.
According to Mohammed Hafez, a visiting professor at the University of Missouri and author of Suicide Bombers in Iraq, the Strategy and Ideology of Martyrdom, the influence of the Saudi Wahabis is key to any understanding of the phenomenon.
His study of 139 suicide bombings found that 53 were carried out by Saudis, compared with 18 by Iraqis, seven by Syrians and four by Jordanians.
The Saudis had already fought foreign jihads in Afghanistan, Bosnia and Chechnya, Professor Hafez said. In Iraq they exploited the culture of martyrdom established by Palestinian suicide bombers. The targeting of so many Shi'ites has been consistent with their beliefs.
"Wahabi tradition sees the ascendancy of Shia as (a) worse evil than occupation by infidels, because Shia are heretics and apostates," he said.
So if Abu Ibrahim went ahead with his journey as planned last week, regardless of his determination to slaughter US soldiers, the chances were he would have been directed towards a Shia target instead. He had no regrets about his impending death: "There is nothing stronger than my love for God and seeking martyrdom," he said brightly.
He has already worded his last message to his wife: "If Allah accepts my martyrdom, then I shall ensure that you are one of those I name to be salvaged and brought to heaven when your time comes."
These then are the factors driving the bombers inexorably onwards. First, fury over the occupation, fuelled by images of the dead on Arab TV stations and fundamentalist websites, and fanned by radical imams who damn the "infidels" and praise al-Qa'ida to the heavens.
Second, burgeoning Wahabism has played into the hands of Sunni extremist groups, directing their attacks increasingly at Iraq's mainly Shia security forces.
Third, the groups know that suicide attacks are easy, cheap and effective. It is hard to defend against them. They terrify the enemy, cow the general population and cast the Government as incompetents, incapable of providing security.
The controllers know they can rely on a volunteer who has come all the way to Iraq for one purpose. They can be sure he is not merely willing but fanatical.
Take Sayeed, our third bomber, who has come to Syria from his home in Jordan. Sayeed studied engineering at university, though he dropped out after a year. Now 32, he runs his own currency exchange business.
It was the hanging of Saddam, whom he regarded as one of the greatest symbols of the Arab world, that made Sayeed resolve to become a suicide bomber. He felt the need to show that "we Arabs have not lost our dignity".
Months of discussion followed with handlers in Amman before Sayeed, a Shi'ite, was admitted to the Sunni network that will smuggle him into Iraq. He has specified that he will have nothing to do with al-Qa'ida.
Sayeed has settled his debts and exonerated his creditors but has said nothing to his well-to-do family of lawyers and businessmen. His parents will get over it, he says. His only targets will be Americans, he insists, like the others. "I'm going there to defend civilians, not to kill them."
But here is the paradox. The bombers are intelligent men whose decisions have entailed much thought, discussion and, in two of the cases above, study.
"These are what I call the violent intellectuals," said Professor Bruce Hoffman, a terrorism expert at Georgetown University, Washington. "They are well educated and highly motivated, two important attributes that ensured success in their education and then business and which will also be useful in ensuring their success as suicide bombers."
This does not mean they have any insight into the big picture in Iraq. They want only to gratify their desire for revenge or glorification on the path to the next world, where at least 70 nymphs will be waiting to give them heavenly fulfilment.
Their impact on the course of the war has nevertheless been devastating, says former CIA officer Robert Baer. "Thanks to the suicide bomber, there is no way the US can defeat the insurgency," he said.
Ahmed has seen at first hand the misery and mayhem the "martyrs" can cause. He does not see that his brother's actions last year and his own mission will achieve little more than prolonging the anguish of Iraq. His mind is made up. You can see it in the intensity of his small, dark eyes.