The movement of Fethullah Gulen, the controversial Turkish cleric who went from being an ally to an enemy of President Recep Tayyip Erdogan, has managed to infiltrate the centers of power, exerting significant influence on institutions and shaping Turkey’s political scene.

Gulen’s movement has long allied itself with Turkey’s Islamist government, deeply infiltrating the country’s police, prosecutors and judiciary, Politico reports in an analysis.

The alliance between Gülen and Erdogan was a “marriage” of convenience while it lasted, until the two sides began to clash with each other and engage in a battle that has shaped the Turkey of today.

The story goes back decades.

President Recep Tayyip Erdogan had risen to power largely thanks to the support of Fethullah Gulen. Gülen’s millions of educated Turkish members have helped fill the ranks of the government, as well as the media, police and courts, helping Erdogan run the country and consolidate his power.

In the early years of Mr. Erdogan’s leadership as prime minister, Gulen’s followers were the government’s most prominent representatives in Turkey and abroad. But a decade later, Mr. Erdogan had grown to resent Mr. G’s reach

How he set up his network

Gülen, born in 1941, was an imam from the Erzurum region in conservative eastern Turkey. He emerged as a leading figure in a movement that began in the 1970s and today influences millions of believers, with a global network of schools, think tanks and media under his umbrella.

As a state-licensed cleric he was sent to the coastal city of Smyrna in the 1960s and began to develop his activity. During this period he founded and financed a network of shared student apartments, preaching to young people and sowing the first seeds of his empire.

Known to his followers as the Hoca efendi (chief preacher), Gülen continued to build a solid base of supporters, forming his sect, called Hizmet Hareketi (Service Movement). By the 1990s, members trained in its network structures had begun to find positions in state institutions.

Although under the watchful eye of the Turkish military, Gülen has tried to maintain close relations with the political and business world. After the collapse of the Soviet Union he established schools in Turkish countries, the Balkans and Africa. While its private schools produced thousands of graduates each year, the movement was also able to gain control of companies in various sectors, including food, health, education and media, thanks to the annual contributions of its followers.

Towards the end of the decade, however, Turkish authorities in a report revealed the movement’s influence on the state apparatus, leading to an investigation by a prosecutor who accused Gülen of “trying to create a theocratic state.”

So on March 21, 1999, Gülen left Turkey for the US — never to return.

Shortly thereafter, Erdogan’s rise to power in 2003 gave the Gülen movement an opportunity to emerge from the shadows with its political influence. The new prime minister had no influence in the state apparatus, and Gulen needed Erdogan to help spread the movement.

The turning point came in February 2012, when a prosecutor asked Hakan Fidan, then head of the National Intelligence Organization, to testify in court about ties between the agency and the Kurdistan Workers’ Party (PKK).

The move to Fidan, Erdogan’s right-hand man at the time, was taken as a direct attack on the prime minister himself.

The first crisis came in 2013 when Gulen’s prosecutors launched corruption investigations against members of Erdogan’s government, including members of his own family.

Then, in December 2013, Istanbul police arrested a businessman, mayors and various sons of government ministers on bribery and corruption charges. Erdoğan’s son, Bilal, is also involved in this case.

Erdogan accused Gulen of leading a “judicial coup” and moved to close some of Gulen’s media businesses, as well as his lucrative tutoring centers that prepared students for university entrance exams.

The 2016 coup attempt

The conflict escalated when members of a group aligned with Gulen — some who visited him in the United States — attempted a military coup in July 2016. Erdogan countered this by taking his supporters to the streets and securing the loyalty of military and intelligence leaders who moved to arrest the coup plotters.

Finally, after the coup attempt against Erdogan in 2016 – in which around 300 people were killed, the Gülen movement was added to Turkey’s list of terrorist organizations as Fetullahist Terrorist Organization.

The Turkish government issued an arrest warrant for Gulen and sought his extradition from the United States, where he had been living in self-imposed exile in Pennsylvania for many years.

Erdogan then called on the US to extradite Gulen, and Washington’s refusal to do so has been a major source of contention between the two countries.

Erdogan never succeeded in bringing Gülen back to Turkey. The United States government cited a lack of evidence to not proceed with the extradition. But he succeeded in crushing the Gülenist movement, labeling it a terrorist organization and jailing many prominent leaders with life sentences without parole.

By the time of his death, Gülen had lost much of his support among families whose relatives were in prison and thousands of others who had been forced to flee Turkey and rebuild their lives as refugees.

After Gülen’s death, Fidan, now foreign minister, declared that he would continue to fight against the movement: “The leader of this dark organization is dead. Our determination in the fight against terrorism remains constant. The news of his death will not lead us to complacency,” he said at a press conference in Ankara this week.

The question now is whether the Gülenists will be able to maintain their strength and extreme tradition of manipulating power behind the scenes with their founder and spiritual leader dead.