Wherever European prosecutors turn these days, as they unravel suspected Islamic terrorist cells and track leads across the Continent, they keep coming across the fingerprints of one man: Abu Musab Zarqawi.
Mr. Zarqawi, a one-legged Jordanian Bedouin currently thought to be hiding in Iran, has emerged as a central suspect in one Al Qaeda-related plot after another, investigators say, from allegedly smuggling suicide bombers into Iraq to orchestrating the recent car bomb blasts in Turkey and planning chemical attacks in Europe.
"He is arguably one of the most dangerous people out there in terms of the number of things he has his hands in," says Matthew Levitt, a former FBI counterterrorism agent now with the Washington Institute for Near East Policy.
"He has a lot of connections to a lot of people, and what makes him most dangerous is his affiliations," Mr. Levitt adds.
Turkish police investigating last November's twin synagogue bombings in Istanbul arrested members of two Islamic groups they said had contacts with Zarqawi. Moroccan investigators concluded that Zarqawi organized and financed last June's quintuple bombing of Jewish and Israeli targets in Casablanca that killed 35 people. Italian and German police recently arrested three men on warrants charging them with helping would-be martyrs to travel from Europe to Iraq, at Zarqawi's behest.
Though intelligence analysts differ over Zarqawi's exact relationship to Osama bin Laden, they agree it has become clear that he has used his leadership of Al Tawhid, a Jordanian extremist group, to develop links not only with Al Qaeda but also with Ansar al-Islam, a radical Kurdish group based in Northern Iraq, the Lebanese Hezbollah, and with North African cells in Europe.
In a mark of his growing importance, the US government put a $5 million price on his head last October, after the Treasury Department named him as a "Specially Designated Global Terrorist." Emphasizing his rising status in jihad circles, Zarqawi issued what appeared to be his first audiotape earlier this month, posting it on the Internet.
In a lengthy tirade against Muslim clerics for not embracing holy war fervently enough, Zarqawi acknowledged the losses his allies have suffered in the US-led war on terror and which seem to have catapulted him to prominence.
"I address you after the approvers and backers [of jihad] have become in short supply, after the wounds have multiplied and the misfortune has worsened, and after many pioneering knights and legendary heroes have passed away," he said on the tape, according to a translation by the US government's Foreign Broadcast Information Service.
He himself has avoided that fate despite frequent and widespread travel since he first appeared on Western intelligence agencies' radar in 1999.
That year Jordanian authorities tied him to an aborted plot to attack a tourist hotel in Amman over the millennium, for which he was later sentenced in absentia to 15 years' hard labor.
"Initially he was geared to national operations in Jordan ... a prize target for regime change" to Islamic radicals seeking to overthrow pro-Western Middle East monarchs, says Magnus Ranstorp, a terrorism expert at St. Andrews' University in Scotland. "But progressively he began acting more internationally, harnessing the diaspora."
In 2000 Zarqawi traveled to Afghanistan, where, according to US intelligence, he ran an Al Qaeda training camp that specialized in chemical and biological agents before being wounded in the leg by a US bombing raid during the Afghan war in 2001. He then fled to Iran, and thence to Iraq, where doctors reportedly amputated his leg and fitted him with a prosthetic limb.
It was that visit to Baghdad that prompted US Secretary of State Colin Powell to cite Zarqawi as evidence of links between Al Qaeda and Saddam Hussein, as he sought to persuade reluctant allies to join Washington in a war to overthrow the Iraqi dictator.
"Iraq today harbors a deadly terrorist network headed by Abu Musab al-Zarqawi, an associate and collaborator of Osama bin Laden and his Al Qaeda lieutenants", Mr. Powell told the UN Security Council last February.
American intelligence officials have said they tracked Zarqawi to a meeting in south Lebanon in August 2002 with Hezbollah leaders, and that he was in Syria in October 2002 when two gunmen assassinated Lawrence Foley, a US diplomat, in Amman.
Those gunmen, arrested soon after the attack, confessed and fingered Zarqawi as the mastermind behind the attack, according to Jordanian Prime Minister Ali Abu al-Ragheb.
Zarqawi is thought to have spent time in and around an Ansar-al Islam camp in the Kurdish region of northern Iraq before last year's US-led invasion of Iraq, and then to have fled across the border to western Iran, where he is believed to be living now.
It is Zarqawi's link to new Ansar cells in Europe that are of most concern to European investigators as they probe alleged terror groups from Germany and Italy to France, Britain and Spain.
Two months ago, German police acting on an Italian warrant, arrested Abderrazak Mahdjoub, an Algerian known as "the sheikh" who Italian prosecutors charge was running a clandestine Ansar network that provided money and false papers to recruits from Europe who wanted to go to Iraq to launch attacks on American troops there.
Italian police simultaneously arrested two men in Milan who they say belonged to the same ring, which they had penetrated by using wiretaps on their phones. Zarqawi, Italian prosecutors allege, sometimes used the same satellite phone that other men in northern Iraq used to contact recruits in Italy.
The exact nature of Ansar al Islam today is a puzzle, Western intelligence analysts say, since its headquarters was destroyed and its members dispersed by US bombs and then by pro-American Kurdish guerrillas last March. But it appears to have evolved considerably from the overwhelmingly local Kurdish organization that it once was.
Evidence suggesting that the group is still active came last week from the CIA, which gave Norwegian prosecutors the transcripts of e-mails it had intercepted from Mullah Krekar, the Kurdish cleric who founded Ansar, allegedly ordering suicide attacks against US troops in Iraq.
Mr. Krekar was under investigation by the police in Norway, where he was granted asylum in 1991, for his alleged role in the murder of a Kurdish politician in 2002. That investigation has now widened to include his suspected role in directing attacks on American occupation forces in Iraq, his lawyer said this week.
Zarqawi's ties to Al Qaeda are also a matter of debate among European and US intelligence agencies. Where once he appeared to be something of a free agent, he seems recently to have identified himself more closely with Mr. bin Laden.
But "whether Zarqawi swore allegiance to bin Laden makes little difference to whether the two would work together at promoting a common agenda," Mr. Levitt said in recent testimony to Congress. "There is no precise organizational or command structure to the assemblage of groups that fall under Al Qaeda's umbrella. Today's international terrorist groups function ... not as tightly structured hierarchies, but rather as shadowy networks that, when necessary, strike ad hoc tactical alliances bridging religious and ideological schisms."
Zarqawi's apparent role as a nexus between several such networks is of particular concern because of his alleged expertise in chemical and biological agents: Men whom authorities link to him were arrested a year ago in London and Paris in possession of small amounts of ricin, a deadly poison for which there is no antidote.
And though European police have thwarted a number of alleged plots over the past two years, "the fact that no Islamic extremist attack has been committed in the European Union [since October 2002] should not be considered as a diminution or an absence of threat," the EU police agency Europol warned in a report last month.
Even as European investigators continue to pursue his lieutenants, Zarqawi himself seems safe for the time being, intelligence experts say, if he stays in his reported refuge in Iran. "He would be a great feather in the cap of the intelligence community if he were captured," says Dr. Ranstorp. "But he is one part of the great intelligence game, and unless Iran is offered an enormous tangible incentive, I doubt we will see him handed over."