Explainer: Who Is Fethullah Gulen?

Fethullah Gulen poses during an interview at his residence in Pennsylvania in March 2014.

Turkish President Recep Tayyip Erdogan and those around him have been quick to blame the country’s foiled coup on what they say is a “shadow state” seeking to overthrow the government.

But if such coded language might be confusing for people outside of Turkey, it was not lost on a 75-year-old Turkish religious leader who lives in the U.S. state of Pennsylvania.

Immediately after the first official Turkish references to a “shadow state,” Fethullah Gulen denied any involvement in the coup effort.

"As someone who suffered under multiple military coups during the past five decades, it is especially insulting to be accused of having any link to such an attempt,” said Gulen.

“I categorically deny such accusations," he added.

But who is Fethullah Gulen and why does Erdogan blame his movement for the coup attempt?

MORE: Cleric Rejects Coup Plot Charges

Gulen, who has lived in exile since 1999 in the United States, is a one-time Erdogan ally who helped the Turkish president’s religiously conservative Justice and Development Party (AKP) come to power in 2002. However, the two allies soon fell out, reportedly over power-sharing issues and over Erdogan’s authoritarian leadership style. In May, Gulen’s movement was designated a terrorist organization in Turkey.

Gulen (left) helped President Erdogan come to power but they later fell out.

A theologian who came to prominence as the leader of Friday prayers in Izmir’s main mosque in the late 1960s, Gulen went into voluntary exile in 1999 when he was accused of trying to undermine the country’s secular state. The charges against him were later dropped in absentia but he has remained in the United States, where he lives as the reclusive leader of one of the Muslim world’s largest religiously based civic organizations. His Hizmet (Service) movement is believed to have millions of followers and sponsors some 1,000 scholastic centers helping high-school students prepare for university exams in 150 countries.

The Hizmet movement, which emphasizes community service in tandem with conservative religious values, is generally considered to be the proponent of a moderate form of Islam. But it also is regarded by some governments as a threat because of the network it weaves among wealthy businessmen and students through its scholastic centers.

The centers are funded by community businessmen and the students often come from poor families, with critics charging that they become easy recruits for a movement which itself has no formal international structure and no official membership lists. Members simply say they work together in a loose alliance because they are inspired by Gulen’s message of public service.

In Central Asia, which initially welcomed the Gulen schools after the collapse of the Soviet Union in 1991, the centers were later taken out of the hands of the Gulen movement amid allegations by the region’s authoritarian governments that they encouraged Islamist activism. But nowhere does the movement come under as much fire as in Turkey, where Erdogan’s government routinely accuses Gulen’s followers of trying to use their positions within Turkish state institutions to undermine the government and usurp power.

Erdogan has previously accused the Gulen movement of being behind several attempts to tar his administration, notably during a police investigation of a 2013 corruption scandal that implicated some of his closest associates. The scandal centered on allegations that officials were enriching themselves by using state funds to buy and funnel gold to Iran to help Tehran evade international sanctions over its nuclear program.

That scandal was followed by the government dismissing many prosecutors and top officials involved in the corruption investigation, with Erdogan telling the public the purge was necessary to protect Turkey from “dark forces” bent upon destroying it. Erdogan last year also succeeded in taking the Gulen schools in Turkey out of the hands of the Gulen movement by appointing government trustees.

With the foiled coup attempt in Turkey, there is now every sign that Erdogan will step up his efforts to destroy the Gulen movement within the country.

The acting chief of staff of Turkey's armed forces, Umit Dundar, said in a statement issued July 16 that the military was determined to remove members of the "parallel structure" from its ranks.

Turkish Prime Minister Binali Yildirim told reporters on July 16 that any country that would harbor Fethullah Gulen would not be Turkey’s friend. He did not specifically name the United States, which Ankara has previously said it hopes will extradite Gulen.

Yildirim also indirectly criticized Washington for not understanding Ankara’s previous expressions of concern about Gulen, saying, “This caused us to pay a big price.”

Washington has not yet responded to the indirect criticism.