RUTHFULLY YOURS

Islamic State’s ability to lure thousands of Westerners is unprecedented in modern history, and may be its scariest success. It is especially disturbing because the bulk of these women and men flocking to Syria are relative newcomers to Islamic observance—a sign the murderous group is gaining appeal well beyond its ultraconservative roots.

Either outright converts from Christianity or people raised in nonobservant or atheist households, they are often rebels in search of a flag of convenience, terrorism researchers say. In rejecting modern society and its rules, many of these newly baked jihadists have embraced Islamic State’s genocidal cult simply because it is the most obvious counterpoint to the West.

Mathieu Guidere, an expert who tracks Western foreign fighters at the University of Toulouse, estimated that more than half are “disillusioned idealists and revolutionaries.”

“They want to remake the world, and find only jihadism as an alternative ideology because there is nothing else left out there,” Mr. Guidere said. “What they are really looking for is armed struggle, and in Islamic State, they find it.”

About one quarter of the 20,000 foreign fighters who traveled to Syria and Iraq hail from Europe, North America and Australia, intelligence officials say. The overwhelming majority are native-born citizens rather than immigrants. This Western influx is orders of magnitude larger than in the earlier battlefields of jihad, such as Afghanistan, Bosnia, Chechnya, or Iraq during the U.S. occupation.

The motives of these Western fighters usually have little to do with Syria nowadays.

“The reason they come here is because they hate their own countries,” said Nidal Salem, a commander with the U.S.-backed rebel group Free Syrian Army who has encountered some European jihadists in the northern province of Aleppo.

Islamic State followers who never make it to the Middle East can be even more dangerous. A case in point is Amedy Coulibaly, the Frenchman who killed five people in Paris last month—four of them in a kosher grocery. On Wednesday, U.S. authorities arrested three Brooklyn men, legal U.S. residents originally from Uzbekistan and Kazakhstan, on charges that they planned to carry out attacks on American soil and join Islamic State in Syria.

Terrorism analysts point out striking similarities between Islamic State’s Western followers—who often come from affluent backgrounds—and the young women and men who embraced homegrown terrorist groups such as the Red Brigades in Italy or Red Army Faction in West Germany in the 1970s and 1980s.

Back then, Communist ideology—despite all the horrors of life in actual Communist countries—still seemed to offer the promise of a better, fairer and purer society. The biggest coup of Islamic State’s propaganda is its capacity to touch a similar nerve with its own utopian vision today, attracting the bored idealists, the misfits, and the adventurers from across Europe. Like the Communists, Islamic State promises universal welfare, free medicine and social justice.

“It is fundamentally the same malaise that is also inspiring the far-left activists,” said Thomas Hegghammer, director of terrorism research at the Norwegian Defense Research Establishment. “A lot of young people have the same idea that the capitalism-centric Western system is not for them, and that another society is being set up.”

For many of them, he added, Islamic State today is the equivalent of the Soviet Union or Cuba in the 1970s, “a place radically different, where you can see a different societal model.”

Unlike al Qaeda, which focused its message on expelling the U.S. and allies from the Muslim world, Islamic State proffers an even more ambitious project of world conquest. It often features images of St. Peter’s Basilica in the Vatican transformed into a mosque, a not-so-subtle attempt to lure recruits with the idea that the group will make Europe part of its caliphate. Some European fighters in Syria and Iraq appear to believe they will come back home with Islam’s conquering armies in the not too distant future.

“We will definitely return and it will not be with pleasantries or stuff like that, but it will be with our weapons and our fighters, and we’ll kill whoever doesn’t accept Islam or doesn’t pay the protective tax,” Abu Qatada, a portly German convert whose real name is Christian Emde, was filmed as saying in a December interview with Jurgen Todenhofer, the only non-Muslim journalist invited to visit Islamic State.

While converts such as Mr. Emde represent only a tiny fraction of Europe’s Muslim communities, they make up about one quarter of the foreign fighters from France, the largest European contributor to Islamic State, and roughly one-fifth in Germany, according to terrorism studies.

One of them, a former German rapper Denis Cuspert, better known under his stage name of Deso Dogg, was named a global terrorist by the U.S. government this month for his role in Islamic State’s recruitment efforts—and for holding up a severed head in an Islamic State video.

The remainder of the Western followers of Islamic State, though raised in Muslim immigrant families, have usually found religion only later in life, often after dabbling with crime, personal setbacks or bouts of depression, terrorism experts say.

Abdurasul Juraboev, 24, one of the three alleged Islamic State followers from Brooklyn, complained to the group’s representative via the Internet that his sisters don’t even know how to wear Islamic head covering, and that his parents engage in “idolatry,” according to the FBI.

A recent study of French youths radicalized by jihadist groups in Syria, conducted by the CPDSI think tank, was based on information provided by families of 160 such young women and men. Some 80% of these families described themselves as atheist. Last month’s Paris attacker, Mr. Coulibaly, while of Muslim origin, was also raised a nonreligious home.

“Most of the French jihadists do not have a real Muslim background, either because they are converts or because they reject, in a born-again dynamic, the religion as practiced by their family and friends,” said Jean-Pierre Filiu, a specialist on political Islam at Sciences-Po university in Paris.

Tailoring its message to this target Western demographic, Islamic State’s propaganda touts the excitement of life in Syria and Iraq over the drab life of dead-end jobs in Europe.

A recent article in its English-language magazine, Dabiq, condemned “the modern-day slavery of employment, work hours, wages, etc.” and praised instead the “noblest income” of booty that can be gained in wars against infidels and heretics.

“A lot of the foreign fighters are young people who are looking for adventure and purpose. They feel a desire to do something,” said Daniel Byman, who co-wrote a recent study on Islamic State’s foreign fighters at Brookings Institution. “To them, a lot of Islamic State’s appeal is that it is badass, and not that it has a particularly sophisticated theology.”