Hargeisa, 12 July 2009- MINNEAPOLIS — The Carlson School of Management rises from the asphalt like a monument to capitalist ambition. Stock prices race across an electronic ticker near a sleek entrance and the atrium soars skyward, as if lifting the aspirations of its students. The school’s plucky motto is “Nowhere but here.”

For a group of students who often met at the school, on the University of Minnesota campus, those words seemed especially fitting. They had fled Somalia as small boys, escaping a catastrophic civil war. They came of age as refugees in Minneapolis, embracing basketball and the prom, hip-hop and the Mall of America. By the time they reached college, their dreams seemed within grasp: one planned to become a doctor; another, an entrepreneur.

But last year, in a study room on the first floor of Carlson, the men turned their energies to a different enterprise.

“Why are we sitting around in America, doing nothing for our people?” one of the men, Mohamoud Hassan, a skinny 23-year-old engineering major, pressed his friends.

In November, Mr. Hassan and two other students dropped out of college and left for Somalia, the homeland they barely knew. Word soon spread that they had joined the Shabaab, a militant Islamist group aligned with Al Qaeda that is fighting to overthrow the fragile Somali government.

The students are among more than 20 young Americans who are the focus of what may be the most significant domestic terrorism investigation since Sept. 11. One of the men, Shirwa Ahmed, blew himself up in Somalia in October, becoming the first known American suicide bomber. The director of the Federal Bureau of Investigation, Robert M. Mueller, has said Mr. Ahmed was “radicalized in his hometown in Minnesota.”

An examination by The New York Times, based on interviews with close friends and relatives of the men, law enforcement officials and lawyers, as well as access to live phone calls and Facebook messages between the men and their friends in the United States, reveals how a far-flung jihadist movement found a foothold in America’s heartland.

The men appear to have been motivated by a complex mix of politics and faith, and their communications show how some are trying to recruit other young Americans to their cause.

The case represents the largest group of American citizens suspected of joining an extremist movement affiliated with Al Qaeda. Although friends say the men have never thought of carrying out attacks in the United States, F.B.I. officials worry that with their training, ideology and American passports, there is a real danger that they could.

“This case is unlike anything we have encountered,” said Ralph S. Boelter, the special agent in charge of the F.B.I.’s Minneapolis office, which is leading the investigation.

Most of the men are Somali refugees who left the Twin Cities of Minneapolis and St. Paul in two waves, starting in late 2007. While religious devotion may have predisposed them to sympathize with the Islamist cause in Somalia, it took a major geopolitical event — the Ethiopian invasion of their homeland in 2006 — to spur them to join what they saw as a legitimate resistance movement, said friends of the men.

For many of the men, the path to Somalia offered something personal as well — a sense of adventure, purpose and even renewal. In the first wave of Somalis who left were men whose uprooted lives resembled those of immigrants in Europe who have joined the jihad. They faced barriers of race and class, religion and language. Mr. Ahmed, the 26-year-old suicide bomber, struggled at community colleges before dropping out. His friend Zakaria Maruf, 30, fell in with a violent street gang and later stocked shelves at a Wal-Mart.

If failure had shadowed this first group of men, the young Minnesotans who followed them to Somalia were succeeding in America. Mr. Hassan, the engineering student, was a rising star in his college community. Another of the men was a pre-med student who had once set his sights on an internship at the Mayo Clinic. They did not leave the United States for a lack of opportunity, their friends said; if anything, they seemed driven by unfulfilled ambition.

“Now they feel important,” said one friend, who remains in contact with the men and, like others, would only speak anonymously because of the investigation.

The case has forced federal agents and terrorism analysts to rethink some of their most basic assumptions about the vulnerability of Muslim immigrants in the United States to the lure of militant Islam. For years, it seemed that “homegrown” terrorism was largely a problem in European countries like Britain and France, where Muslim immigrants had failed to prosper economically or integrate culturally. By contrast, experts believed that the successful assimilation of foreign-born Muslims in the United States had largely immunized them from the appeal of radical ideologies.

The story of the Twin Cities men does not lend itself to facile categorizations. They make up a minuscule percentage of their Somali-American community, and it is unclear whether their transformation reflects any broader trend. Nor are they especially representative of the wider Muslim immigrant population, which has enjoyed a stable and largely middle-class existence.

Even among the world’s jihadists, the young men from Minneapolis are something of an exception: in their instant messages and cellphone calls, they seem caught between inner-city America and the badlands of Africa, pining for Starbucks one day, extolling the virtues of camel’s milk and Islamic fundamentalism the next.

“Allah will never change the situation of a people unless they change themselves,” Mr. Hassan, the engineering student, wrote in a Facebook message he posted on April 15. “Take a sec and think about your situation deeply. What change do you need to make?”

Generation of Refugees

Shirwa Ahmed climbed the worn, concrete steps of Roosevelt High School on his first day as a freshman in September 1996.

A slim boy with a watchful gaze, he was one of hundreds of Somali teenagers who had landed at the school in southeastern Minneapolis. Some had never seen a drinking fountain. Others did not know how to hold a pencil, recalled the school’s principal, Bruce Gilman. They carried unspeakable traumas. A number of the students had witnessed their parents being killed.

“It’s almost unimaginable what some of these kids went through,” Mr. Gilman said.

The country they had fled, on the eastern tip of Africa, was embroiled in a civil war that had left it without a functioning government since 1991.

The anarchy reached American televisions two years later, when warlords shot down two Black Hawk helicopters, killing 18 United States soldiers. By then, tens of thousands of Somalis had died and a mass exodus had begun.

A generation of Somalis grew up in the overcrowded refugee camps of northern Kenya, where malaria, scorpion infestations and hunger took their toll. Tales of America sustained them. Clean water was said to flow freely in kitchens, and simple jobs like plucking chickens paid handsomely.

Proof came in the cash sent by a first wave of refugees who had arrived in the United States in the early 1990s. Minneapolis, with its robust social services and steady supply of unskilled jobs, quickly became the capital of their North American diaspora.

When they ended their shifts as cabdrivers or janitors, many Somalis retreated from American life. They had transformed a blighted stretch near the Mississippi River into a Little Mogadishu, commandeering a grim collection of cinderblock buildings known as the Towers — a onetime fictional residence of the heroine of “The Mary Tyler Moore Show.”

They cut their hair at Somali barber shops, prayed at Somali mosques and organized themselves along the same clan lines that had divided them for decades, calling on tribal elders to settle family disputes and community rifts.

If the adults kept their distance from American culture, their children had little choice but to dive in.

At Roosevelt, Mr. Ahmed was a quick study. He memorized Ice Cube’s lyrics. He practiced for hours on neighborhood basketball courts. He took note of the clothing and vernacular of his African-American classmates, emulating what he could.

His pants sagged, but never too much. He spoke of “homeboys” and used the “n” word, but gave careful regard to the school’s rules. When a classmate’s purse was stolen, it was Mr. Ahmed who dutifully turned in the thief.

Much as he tried, he failed to fit in.

You’re not black, his peers taunted. Go back to Africa.

Somali and African-American students clashed frequently at the school, but Mr. Ahmed seemed ill-suited to the fight. Taciturn by nature, he recoiled at the taunts, his close friend Nicole Hartford said.

“How can they be mad at me for looking like them?” she recalled him saying. “We’re from the same place.”

Even as Mr. Ahmed met rejection at school, he faced disapproval from relatives, who complained that he was mixing with “ghetto people,” Ms. Hartford recalled. It was a classic conundrum for young Somalis: how to be one thing at school and another at home.

Developments in the homeland, followed obsessively by the adults, held little interest among teenagers. They rolled their eyes at the older men known as “the sitting warriors,” who debated clan politics with such gusto at one Starbucks that the staff bought a decibel meter to ensure that the noise did not rise above legal limits.

Yet young men like Mr. Ahmed remained tethered to Somalia by the remittances they were pressed to send. After school every day, he joined a stream of teenagers headed for the airport, where he pushed passengers in wheelchairs. He sent half of his income to Somalia, to “relatives we don’t even know,” his friend Nimco Ahmed said.

The war had torn families apart, and fathers were in short supply. Somali boys struggled most visibly. The financial strain on families like Mr. Ahmed’s, which was headed by an older sister, proved staggering. Of the estimated 100,000 Somalis in the United States, more than 60 percent live in poverty, according to recent census data.

After graduating from high school in 2000, Mr. Ahmed seemed to flounder, taking community college classes while working odd jobs, friends said. But he had done better than many peers, who turned to crime and gangs like Murda Squad and Rough Tough Somalis.

At the root of the problem was a “crisis of belonging,” said Mohamud Galony, a science tutor who was friends with Mr. Ahmed and is the uncle of another boy who left. Young Somalis had been raised to honor their families’ tribes, yet felt disconnected from them. “They want to belong, but who do they belong to?” said Mr. Galony, 23.

By 2004, Mr. Ahmed had found a new circle of friends. These religious young men, pegged as “born-agains” or “fundis,” set themselves apart by their dress. Their trousers had gone from sagging to short, emulating the Prophet Muhammad, who was said to have kept his clothes from touching the ground.

Perhaps none of Mr. Ahmed’s contemporaries had undergone a transformation like that of Zakaria Maruf.

A short boy prone to fits of rage, Mr. Maruf began running afoul of the law at the age of 14. For a time, he fell in with the Hot Boyz, a violent street gang.

He seemed to crave recognition. Known on the basketball court as Zak, he was a mediocre athlete, but he pushed himself harder than anyone else, recalled his coach, Ahmed Dahir.

Mr. Maruf threw himself into Islam with the same intensity, becoming a fixture at a mosque near the Towers, where he mastered the call to prayer. “He had an ego the size of Minnesota,” one fellow mosque member said. “It was, ‘Look at me.’ ”

Mr. Ahmed and Mr. Maruf were sometimes seen preaching to kids on the street, offering their own lives as examples of reform. Yet they continued to struggle.

Mr. Maruf’s criminal record had foiled his search for a job. When he proposed to a young woman in 2005, her parents scoffed, one friend recalled. They did not want their daughter winding up “on welfare,” they told Mr. Maruf, who worked at a Wal-Mart.

“They think that life is about money and material things, but watch what that will do for them,” Mr. Maruf told the friend one afternoon, sitting slumped at the mosque.

He seemed to be searching for a clean slate. Both he and Mr. Ahmed would find it thousands of miles away.

A Political Awakening

In 2006, an Islamist movement swept through Somalia and seized control, giving the country its first taste of peace in a generation.

The group, known as the Islamic Courts Union, promised to end 15 years of internecine violence by uniting Somalia’s clans under the banner of Islam. Key ports were reopened, and order was restored to the capital, Mogadishu.

In Washington, officials of the Bush administration saw a threat to East African stability. Hard-line factions of the Courts were thought to be sheltering Qaeda operatives and had declared a jihad against neighboring Ethiopia, a predominantly Christian country. In December 2006, Ethiopian troops crossed the border and routed the Islamist forces with intelligence support from the United States, beginning a two-year occupation.

These events triggered a political awakening among young Somalis in Minneapolis. They had long viewed their homeland’s problems as hopelessly clan-based, but the Ethiopian campaign simplified things. Here was an external enemy against which young Somalis could unite.

Spurred by a newfound sense of nationalism, college students distributed T-shirts emblazoned with the Somali flag and held demonstrations during a frigid Minnesota winter.

The protests took on a religious dimension as well. While the United States had defended the Ethiopian invasion as a front in the global war on terrorism, many Somalis saw it as a Christian crusade into a Muslim land. They were outraged at reports of Ethiopian troops raping Somali women, looting mosques and killing civilians.

If the Ethiopians were seen as infidel invaders, an insurgent group known as the Shabaab — “youth,” in Arabic — was emerging as “freedom fighters.” In its online propaganda, the Shabaab conflated nationalist sentiments with religious ideology, following a tactic honed by Al Qaeda.

The Shabaab began releasing videos portraying Somalia’s struggle as part of a global movement to defend Islam and restore its rule. Foreign recruits were promised “victory or martyrdom” for enlisting. Several American converts to Islam joined up.

The recruitment of the Twin Cities men can be traced to a group of Somali immigrants from Northern Europe and other countries who, in 2005, traveled to Somalia to fight with the Islamist movement, a senior law enforcement official said. A handful of those men later went to Minneapolis, the official said, and helped persuade the first large group from the Twin Cities to leave for Somalia starting in late 2007.

That first wave consisted of men in their 20s and 30s who had been fixtures at the Abubakar As-Saddique Islamic Center, the largest Somali mosque in Minneapolis. They included an emergency medical technician, a former waiter, a car-rental employee and Shirwa Ahmed, the onetime Roosevelt student who now wore a thick beard and silk gown.

That fall, Mr. Ahmed announced to friends that he was moving to the Middle East to study Islam. After he left for Saudi Arabia to make hajj, the obligatory pilgrimage to Mecca, his nephew wrote to a friend, “My uncle is a changed man.”

The following spring, Zakaria Maruf, the former gang member, vanished. Shortly after his disappearance, two teenage boys walked into a travel agency near the Towers, clutching their Somali passports, recalled Abia Ali, an accountant at the agency.

Ms. Ali recognized the boys from the mosque and suspected that they planned to follow Mr. Maruf to Somalia. She warned the mosque’s leaders, who alerted the boys’ parents and then summoned a meeting with the mosque’s young members.

“All this talk of the movement must stop,” the imam, Sheikh Abdirahman Sheikh Omar Ahmed, recalled telling the crowd. “Focus on your life here. If you become a doctor or an engineer, you can help your country. Over there you will be a dead body on the street.”

In the audience were several young men who would soon disappear.

‘Our Best Kids’

If the first men who left for Somalia had struggled to find their place in America, the boys to follow were “our best kids,” in the words of one uncle.

Mohamoud Hassan outdid most of his peers at Roosevelt High School in 2006, becoming one of the few Somali boys to make it to college that year.

He stood out at the University of Minnesota. Answering to the nickname Snake, the tall, lanky freshman wore a black cotton beret and a pencil-thin moustache. Women found him clownishly charming, occasionally giving in to his pleas for their “digits.” The engineering major tried to cultivate a more serious image, writing poetry, debating politics and poring through “The Autobiography of Malcolm X,” his friend Hindia Ali recalled.

Even his closest friends found Mr. Hassan an enigma. He had come to the United States without parents or siblings and looked after his ailing grandmother in a dim apartment in the Towers. He longed to return to his homeland, both to experience it for himself and to rebuild it. It was a common obsession among his friends. “It’s just this missing piece of us,” his friend Ruqia Mohamed said.

After the Ethiopian invasion, a circle of listeners sometimes gathered around Mr. Hassan at the Coffman student center. Mr. Hassan, then the vice president of the Minnesota Somali Student Union, defended the occupation, posting an essay on Facebook assailing the insurgents as “a handful of thugs.”

But over time, he began to see things differently.

Mr. Hassan’s interest in the Islamist movement dovetailed with his own religious transformation, friends said. In the fall of 2007 he began downloading sermons onto his iPod and soon was attending the Abubakar mosque.

By then, Mr. Hassan had become upset by the reports of rapes in Somalia and set out to learn more about the insurgency, one friend recalled. He began talking of joining the movement as early as February 2008, around the same time that a friend from the mosque — Mr. Maruf, the former gang member — left for Somalia.

“I wanted to go, so I got to know him,” Mr. Hassan said in a recent telephone conversation from Somalia with a Minneapolis friend.

That May, he was incensed by a United States military air strike that killed Aden Hashi Ayro, a leader of the Shabaab, along with at least 10 civilians. “How dare they?” Mr. Hassan demanded one afternoon at the student center. “Who is the terrorist?”

Mr. Hassan and another university student searched the Internet for jihadist videos and chat rooms, the friend said. They listened to “Constants on the Path to Jihad,” lectures by the Yemeni cleric Anwar al-Awlaki, who is suspected of inciting Muslims in the West to violence.

While Somali nationalism had initially driven the men, a friend said, their cause eventually took on a religious cast. They became convinced that Somalia’s years of bloodshed were punishment from God for straying from Islam, the friend said. The answer was to restore the Caliphate, or Islamic rule.

“They saw it as their duty to go and fight,” the friend said. “If it was just nationalism, they could give money. But religion convinced them to sacrifice their whole life.”

Over the next few months, the men communicated frequently with Zakaria Maruf, who was then in southern Somalia trying to recruit men in Minneapolis to join him, said a senior law enforcement official and a lawyer, Stephen L. Smith, who represents one of the men Mr. Maruf approached.

Mr. Maruf reached out through listservs and conference calls arranged by a teenage boy who distributed 800 numbers and passwords so people could listen in. Mr. Maruf had little trouble finding an audience for his pitch in the Twin Cities; he had shuttled boys from the Abubakar mosque to basketball games, and a recording of his call to prayer was a ring tone on the cellphones of young Somalis.

In his calls, listeners heard him boast that he had gotten married, had a child and become a governor for the Shabaab. The onetime stock boy with a criminal record was now a figure of authority, if one believed his claims.

“He was the ‘I’ll take you to the battlefield’ person,” one acquaintance said.

Despite all the spirited talk of the jihad, Mohamoud Hassan, the engineering student, seemed to waver, friends recalled. The tipping point, one said, may have come that September when a close friend was shot dead outside a youth center — the fifth slaying of a young Somali in the Twin Cities in a year.

“I used to think that death only happens to old people,” Mr. Hassan told his friend Ruqia Mohamed. “But he was young — my age. I guess I could die tomorrow.”

Mr. Hassan began spending much of his time with a small group of men that included a pre-med student, an electrical engineering student, a white 27-year-old convert and a pesky 17-year-old Roosevelt senior. The boy, known as Little Bashir, had memorized the Koran and talked of going to Harvard.

The men acted secretive, friends recalled, meeting alone in a study room at the Carlson building, where Mr. Hassan and the pre-med student worked as uniformed security personnel.

In late October, the group visited University Travel Services, near the Towers, accompanied by an older man with a gray beard who introduced himself as their uncle, the manager of the agency said in an interview.

The “uncle” explained that the men wanted to buy tickets to Somalia, and were waiting for passports. Soon after, the young men returned by themselves and paid cash for their tickets, roughly $1,800 apiece, the manager said.

They left on different days to avoid drawing attention, a friend said. Mr. Hassan drove to Chicago, where he boarded a plane to Dubai on Nov. 1, according to an itinerary obtained by The Times. By the eve of the United States presidential election three days later, all of the men were gone.

Training for Jihad

As word spread in Minneapolis that a new group of men had disappeared, another piece of jarring news came from Somalia: Shirwa Ahmed had blown himself up. On Oct. 29, 2008, he drove a car packed with explosives into a government compound in Puntland, a region of northern Somalia.

The bombing was among five attacks that day coordinated by the Shabaab, which left more than 20 people dead in the group’s campaign to eliminate enemies and show their might. The F.B.I. investigated and sent Mr. Ahmed’s remains to Minneapolis in November.

By then, Mr. Hassan and his friends were journeying in the opposite direction. A close friend said the men were met by Zakaria Maruf, the recruiter, and taken to the southern port city of Merka, where they stayed in a “welcoming house” run by a Somali woman whom the men called Mama.

By January, most of the men were at a training camp in southern Somalia, following a strict routine that Mr. Hassan and others described to their Minneapolis friends in phone calls. They woke before dawn to pray and study the Koran. They engaged in rigorous training, running obstacle courses and learning to make bombs.

As foreign recruits, they received special treatment. These mujahideen slept in a different bunker and were considered to have a higher status, the friend said.

Mr. Hassan was struck by the diversity of the fighters, who included Chechnyans and converts from Europe. “I am looking out into the field and I see so many different colors,” Mr. Hassan told the friend by phone.

If becoming a jihadist usually means parting with life in the West, the men from Minneapolis soon broke with tradition. They frequently communicated with dozens of friends in the United States whom one acquaintance described as “the homeys they left behind.”

Two friends showed The Times the Facebook communications of four of the men, including one whose profile picture was, until recently, of Osama bin Laden.

One exchange on Facebook distilled the push and pull: “’Sup dawg,” one of the men wrote to a friend in late December. “Bring yourself over here” to “M-town,” the message continued, where the men carry “all types of guns.”

“I ain’t goin’ over there man,” the young man answered. “Dats the same reason we came 2 America Locco.”

Mr. Hassan and the others claimed to be enjoying their adventure. They had grown up hearing tales about the winding Shabelle River in southern Somalia and the rich taste of camel milk. When they finally swam in the river and drank the milk, they called their friends in Minneapolis, their voices dreamy.

The men seemed to revel in their new identity as fighters. One day in March, Mr. Hassan’s friend the pre-med student was talking on the phone with someone in Minneapolis when he opened fire with his AK-47. He was checking “to see if it worked,” the person recalled him saying.

But there were cracks in the men’s bravado. While on a boat headed to a Shabaab stronghold in the south, the high school student known as Little Bashir began vomiting so violently that he lost his glasses, his mother said in an interview. After he told her this by phone, she fetched his prescription and read it to him, hoping he would somehow find an optometrist.

It was hard to imagine this 17-year-old — a frail, bookish boy who had delighted in calculus — making his way through war-ravaged Somalia, friends of his said.

“I doubt that he could even pick up a handgun,” said Mr. Galony, who had tutored the boy in chemistry.

If the others seemed hardier, they still had moments of weakness. They missed movies and basketball, deodorant and boxer shorts, they told friends back home. One of the men, who suffered from heartburn, asked if anyone could send him a box of Tums by DHL.

Their longing for life in America came and went. They encountered more serious challenges in Somalia. By the time some of them entered training, the Shabaab was fast losing popularity. The Ethiopian troops had pulled out, making way for a new Somali president, Sheik Sharif Sheik Ahmed, the same man who had once led the Islamist movement to which the Shabaab formerly belonged.

“Some of them wondered who they were fighting,” one friend said.

The jihadists’ conversations with their Minneapolis friends sometimes turned testy. Two of the friends said in interviews that they, like many Somalis, had become sharply critical of the Shabaab. The group has carried out beheadings, amputations and the fatal stoning of a 13-year-old rape victim.

In April, the Shabaab fired several mortar rounds at a plane carrying Representative Donald M. Payne, a New Jersey Democrat who was leaving Somalia after meeting with the president.

“What, are y’all retarded?” one of Mr. Maruf’s friends, a college student, chided him in a phone call. “He’s our only friend in Congress.”

“You have been brainwashed by the media,” Mr. Maruf shot back.

Later, the student thought back on the conversation. “Sometimes they will talk and you’re like, Are you trying to prove this to me or to yourself?” she said. “They have this inner struggle.”

An Inquiry Intensifies

Ralph S. Boelter had a robust résumé by the time he took over the F.B.I.’s Minneapolis office in early 2007. He had worked on white-collar crimes in Boston and violent gangs in Los Angeles. He had investigated the leak of the C.I.A. officer Valerie Wilson’s identity.

Returning to the Midwest put Mr. Boelter, a square-jawed Wisconsin native, back on familiar ground. But less than two years later, he found himself tasked with one of the most complex terrorism cases since Sept. 11.

“Never did I imagine that I would step into this here,” Mr. Boelter said one recent afternoon.

In the years since the Sept. 11 attacks, Somalis had remained largely under the law enforcement radar while other Muslim immigrants — primarily Arabs and South Asians — experienced the brunt of the raids and scrutiny.

While federal investigators had tracked the movements of American recruits to the Shabaab since at least early 2008, the F.B.I.’s case did not swing into high gear until after Shirwa Ahmed’s suicide attack that fall.

Investigators in Minneapolis approached Somalis on the street, in their homes, at the Abubakar mosque and on the University of Minnesota campus. Brandishing photographs, the agents asked questions about community figures like the imam of the mosque and its youth director.

As the inquiry wore on, community leaders say, more than 50 people were subpoenaed to appear before a federal grand jury in Minneapolis and another jury was convened in San Diego. In April, F.B.I. agents raided three Somali money wiring businesses in Minneapolis. By then, the investigation had expanded to smaller Somali communities in Boston; Seattle; Portland, Me.; and Columbus, Ohio.

Somalis in Minneapolis, by turns frightened and intrigued by the inquiry, came up with a Somali code name for the F.B.I. agents in their midst: Fadumo Bashir Ismael.

Mr. Boelter tried to counter the negative attention by appearing on Somali television and radio, encouraging people to cooperate with investigators. Yet he has revealed little about the case itself. The scope and intensity of the investigation, he said, is merely commensurate to the danger posed by the men.

“If American citizens are joining the Shabaab, the potential threat domestically is serious,” Mr. Boelter said. “I think they could be commissioned to come back. Or they could do it on their own because they are philosophically aligned with the Shabaab or Al Qaeda.”

Senior Qaeda leaders have aggressively promoted Somalia as the latest destination for foreign fighters, said Evan Kohlmann, a terrorism consultant who frequently works for the government. In recent months, a small number of Qaeda operatives have reportedly sought sanctuary there.

Analysts find the alliance troubling because Al Qaeda has long sought recruits with American and European passports who can cross borders more freely, said Bruce Hoffman, a professor at Georgetown University who studies terrorism.

There are indications that three Twin Cities men have returned, possibly after defecting from the Shabaab. A friend of the men still in Somalia said they had no thought of attacking America. “Why would I do that?” the friend recalled the pre-med student, Adbisalan Ali, saying on the phone last spring. “My mom could be walking down the street.”

The central question driving the F.B.I. investigation is whether United States citizens have provided material support to the Shabaab, either in the form of personnel or money. Three local acquaintances of Mr. Maruf, the recruiter, sent him small amounts of money at his request, according to one of the friends and a lawyer for the others. It is not known how the young men who followed him to Somalia paid for their trips. Two of the teenage boys were seen knocking on doors at the Towers last summer, asking for donations for “an orphanage.”

The full dimensions of the recruitment effort also remain unclear. A close friend of several of the men described the process as “a chain of friendship” in which one group encouraged the next.

“They want to bring people they are close with because they need that familiarity,” the friend said. “They created their own little America in Somalia.”

The manager of University Travel Services said that since November, he had turned away at least 20 men looking to buy tickets to Somalia, adding that the requests had slowed considerably. Meanwhile, some Somali parents in the Twin Cities have taken to hiding their sons’ passports.

The tension in the community has turned inward at times. Last March, the uncle of Burhan Hassan, the boy known as Little Bashir, testified at a Congressional hearing on the case that the mosque had been “brainwashing” the young men and had possibly raised money for the Shabaab.

The mosque’s leaders denied this, in turn accusing the family and others of shirking responsibility for their own children. “That’s their obligation, to know where their kids are going,” said Omar Hurre, the mosque’s executive director.

A Struggle to Understand

For many older Somalis in Minnesota, the deepest mystery is why so many young refugees would risk their lives and futures to return to a country that their parents struggled to leave.

The mother of Burhan Hassan had been trying to persuade him to escape to the United States Embassy in Nairobi, Kenya, said the uncle, Osman Ahmed.

The boy had been calling from Somalia, telling her that he was “fine” and that he missed her cooking. “There is no future for me in America anymore,” she recalled him telling her. “If I come back they’ll send me to Guantánamo.”

But he finally agreed to leave, and in late May his mother wired him about $800, Mr. Ahmed said. Ten days later, on June 5, she picked up the telephone to learn that her son was dead.

He had been shot in the head, a stranger on the phone told Mr. Hassan’s mother. Some of the boy’s relatives suspect that he was killed to prevent him from cooperating with the American investigation. F.B.I. officials have declined to confirm Mr. Hassan’s death.

Months have passed since the older members of his group completed their training in Somalia. Lately, they seem “hardened” and at times radical, a Minneapolis friend said.

During one call, the friend asked Mohamoud Hassan, the engineering student, what it was like to kill people. He told of getting “an adrenaline rush,” the friend recalled, and joked that he and his friends compared “body counts.”

Two weeks ago, they spoke again and the conversation turned to the killing of Little Bashir. One of the men had referred to his passing as “martyrdom” in a recent Facebook posting.

Mr. Hassan seemed to agree.

“Allah knows how to pick,” he said. “The family’s feeling sad, but we’re feeling happy for him.”

Source: The New York Times