Aides say Gulen stays in a small apartment atop a modern three-story house, one of 10 buildings on the bucolic property. He has gone out the front gate, past the stately oak and cedar trees, only a few times since he moved here in 1999 just ahead of a treason charge back in Turkey.

The recluse enjoys his "quiet and tranquil" refuge in this tiny Pocono Mountains town, where he can "avoid stress and legal harassment" in Turkey, Alp Aslandogan, an informal spokesman, said as he led a tour of the campus-like compound. Back there, he added, are "many people who love him, and many who don't."

One who clearly doesn't is Turkey's prime minister, Recep Tayyip Erdogan, who blames the cleric for the political upheaval that threatens his hold on power. A harsh government crackdown on opponents, including many who follow Gulen's educational and cultural movement, has chilled Erdogan's once warm relations with the White House.

Gulen preaches an unusual mix of Islamic piety and Sufi mysticism, as well as free markets, democracy and religious tolerance. His followers have built a worldwide religious, social and nationalistic movement, known as Hizmet, in his name. They control a network of schools, companies and charities around the globe, including about 120 schools and scores of nonprofit groups in the United States.

Gulen's following is especially potent back home. Inspired in part by sermons on his website, his supporters in the Turkish police and judiciary, backed by allies at the country's largest newspaper, are pushing a corruption investigation into Erdogan's inner circle that has sparked a bitter political power struggle.

The wide-ranging inquiry already has caused three Cabinet ministers to resign and led to dozens of arrests. The economy has taken a hit and the lira, the national currency, fell to a record low against the dollar in the last week.

Erdogan, who once embraced Gulen as a close political ally, has launched an escalating series of counterattacks. The government has closed Hizmet schools and fired 2,000 police officers deemed loyal to the cleric. Erdogan also has announced plans to place the appointment of judges, which Gulen allegedly influences, more under government control.

On Thursday, after prosecutors sought to press graft charges against Erdogan's son Bilal, the government removed 20 top prosecutors from their posts. Officials also opened criminal investigations into three prosecutors who have led the corruption inquiry.

Turkish authorities accuse Gulen and his movement of secretly creating an unaccountable "state within a state" that is trying to foment a "judicial coup." His movement denies he is behind the graft inquiry or antigovernment protests in the streets. They insist he supports democratic reform and interfaith dialogue, not violence.

The political strife in a strategic U.S. ally has put the Obama administration in a difficult position.

Erdogan, who has led the government in Ankara since 2003, was long lauded for turning Turkey into a model of Islamic democracy.

Turkey also is host to Incirlik air base, a key U.S. Air Force installation.

Last May, when Erdogan visited the White House, President Obama stood by his side and told reporters, "I value so much the partnership that I've been able to develop with Prime Minister Erdogan."

The crackdown in Turkey that began in June has upended that relationship. Erdogan has charged that the corruption inquiry is part of a foreign plot to destabilize the nation, and that Washington is complicit with Gulen. Ankara has threatened to expel U.S. Ambassador Francis J. Ricciardone.

The State Department has sought to avoid inflaming the situation. Spokeswoman Jen Psaki said "we continue to follow the ongoing corruption investigations in Turkey" and the United States "supports the desire of the people of Turkey for a legal system that meets the high standards of fairness, timeliness and transparency."

James Jeffrey, who served as U.S. ambassador to Turkey from 2008 to 2010, is critical of Gulen's role in the political tumult.

Gulen "has a political movement that has infiltrated the police and military and is able to use their government powers to political ends," Jeffrey said. Even if the corruption charges are true, "they are politically motivated and that's wrong."

Gulen's direct role is difficult to pin down. By all accounts, he does not manage his movement's day-to-day business affairs, devoting himself primarily to prayer and religious study. A short man with a white mustache, he chiefly communicates via his Internet sermons and scores of books he has published.

Unlike the Ayatollah Ruhollah Khomeini, who spent 14 years in exile from Iran before he was swept to power in the Islamic Revolution of 1979, or the Dalai Lama, who has lived in India since fleeing Chinese-controlled Tibet in 1959, Gulen avoids the media and makes few public appearances.

Experts who have studied Hizmet describe it as secretive, partly because it emerged as an opposition force during an era of repressive military rule in Turkey. And his self-imposed exile in the hills of northeastern Pennsylvania has spawned conspiracy theories.

"His movement is very opaque in nature," said Soner Cagaptay, director of the Turkish Research Program at the Washington Institute for Near East Policy. "It flourished as an underground movement in the 1980s and '90s under military rule, and there is a deep-rooted memory of operating in an opaque manner in order to survive. Even those in the U.S. are not entirely transparent."

The Hizmet movement is surprisingly widespread in the U.S., where Gulen has permanent resident status. Hizmet operates nonprofit groups across the country devoted to social services, education and promoting Turkish culture. They include the Pacifica Institute in Los Angeles and six other California cities, and the Niagara Foundation in Chicago, which has branches in eight other states.

The movement also supports more than 120 publicly funded charter schools in about two dozen states.

The U.S. schools do not teach religion, and many are highly regarded academically. But state and federal authorities are investigating Hizmet schools in Ohio, Louisiana, Alabama, Texas and elsewhere for improper use of public funds and for allegedly importing Turkish teachers without proper visas, among other complaints. The inquiries have led to the repayment of public funds in some cases.

Born in eastern Turkey, Gulen is said to have memorized the Koran by age 12. In the 1970s, he developed a following when he began distributing tapes of his sermons, largely based on the Sufi branch of Islam best known in the West for the dervishes who whirl themselves into religious ecstasy.

Soon he opened private schools in Turkey to prepare children of religious Turks for college exams. By the 1990s, his followers had expanded that network into a diversified business empire.

Gulen left Turkey for medical treatment just before he was accused of plotting to overthrow the secular government. He was acquitted after being tried in absentia in 2008, but never returned.

Here in Saylorsburg, about 85 miles west of New York, about two dozen followers are regular guests at the Gulen compound. The numbers swell to about 100 on Fridays, the Islamic holy day, when the cleric often delivers a sermon.

If not for the Turkish protesters who periodically demonstrate outside the front gate, and the hearty dinner the compound hosts for its neighbors each autumn, the scholar's presence might go unnoticed in the community.

"I've lived here all my life, but I've never seen him," said a 56-year-old woman who resides close to the compound and who declined to give her name. "They tell us that he's here."

Gulen declined an interview request. In a rare interview last year with the Atlantic magazine, he downplayed his influence.

"I don't have a need to promote myself," he said. "I've never sought to be known or recognized by people. I simply share ideas I believe in with people around me.... My core belief is to seek peace in the world, helping people eliminate certain malevolent attitudes through education as much as possible."