The photograph shows a young man sporting a red-and-white chequered head-dress, a wispy beard and a zealot's eyes. Majed Hamoud Mubarak al-Harithy, a 23-year-old student from the Saudi Arabian city of Mecca, was smuggled into Iraq from Syria sometime before August 2007. He was carrying a passport, 252 Saudi riyals (£35) and US$101, and was eager to become a “martyr”.

Al-Harithy has almost certainly achieved his goal by now. Al-Qaeda, the group he reported to, carried out more than 4,500 attacks against Iraqi civilians last year, killing 3,870 people and wounding nearly 18,000, according to figures just released by the US military in Baghdad. It also claimed that 90 per cent of al-Qaeda's suicide-bombers were foreigners like al-Harithy.

Rear Admiral Gregory Smith, a spokesman, said that the US military had gained a much better understanding of the terrorists it was fighting thanks to a treasure trove of biographical records that US troops discovered during a pre-dawn raid on some tents pitched near the town of Sinjar, on the Syrian border, last October.

Those records gave details of more than 600 foreign fighters who were smuggled into Iraq to join al-Qaeda in the 12 months leading up to August 2007. They included photographs of many of the men — gnarled and fresh-faced, scowling and smiling, bearded and clean-shaven — as well as ages, nationalities, home towns, relatives' telephone numbers, aliases and other details.

An analysis of those records, and the records themselves, have recently been published by the Combating Terrorism Centre at West Point, the US military academy, and offer probably the most accurate picture yet of the foreign fighters who have poured into Iraq over the past few years.

More than 40 per cent were Saudi Arabians, but almost as many came, surprisingly, from North African countries such as Morocco, Algeria and Tunisia. Nineteen per cent came from Libya alone, including 52 fighters came from the coastal town of Darnah (population 80,000).

The youngest fighter was a Saudi boy named Abdallah Abid al-Sulaymani who was only 15 when he reached Iraq. The oldest was 54, but the average age was 24 to 25, suggesting that most were new recruits. Of the 157 who listed their occupations, 43 per cent said they were students. There were also five teachers, four engineers, three doctors and one “massage therapist”.

The records also listed the recruits' designated roles in Iraq: 56 per cent were to be suicide-bombers and 42 per cent were to be fighters. A couple were allocated to media operations.

Admiral Smith said that greater co-operation by Syria and Saudi Arabia had halved the number of foreign fighters entering Iraq to perhaps 40 or 50 a month in the past year. Al-Qaeda attacks, which peaked last March and April, have also declined significantly since the US troop surge took effect in the second half of the year and Sunnis in large swathes of Iraq turned on the al-Qaeda extremists in their midst.

The New York Times says that the Pentagon is considering making General David Petraeus, the US commander widely credited with the coalition's recent successes against al-Qaeda, Nato's supreme commander this autumn.

Admiral Smith said that al-Qaeda remained a force in the northern city of Mosul, areas around Kirkuk, Diyala province, and south of Baghdad. But Operation Phantom Phoenix, which US and Iraqi forces launched against the remaining al-Qaeda strongholds on January 8, had so far killed 121 al-Qaeda terrorists, discovered 351 weapons caches and found three bomb factories. One US military intelligence analyst claimed that al-Qaeda had become a harder target to hit because it was “in an almost constant state of fleeing”.

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