Several former soldiers appear to have confessed that they had been FETO members for a considerable amount of time, sometimes as early as military high school, and that Gulen was behind the coup attempt.
Indeed, nine months after the coup attempt, numerous investigations in public prosecution offices across Turkey have permitted to better understand what happened on July 15 and to file more than 100 cases against FETO.
The following information comes from all the evidence amassed by various Turkish officials. No one has yet been convicted in relation to the July 15 coup attempt.
On March 8, a court in Ankara accepted the indictment against the main suspects in coup attempt, and the trial is due to start on May 22.
Prominent defendants include Ali Yazici, the former military aide to President Recep Tayyip Erdogan; Levent Turkkan, Chief of General Staff Gen. Hulusi Akar’s former aide; and Muhammet Uslu, a former official in the prime minister’s private office.
Adil Oksuz, regarded as the main coup plotter after Gulen, was at Akinci 4th Main Jet Base Command, near the capital Ankara, on the night of the coup attempt.
Oksuz is said to be a key figure in the coup attempt serving as an "imam" to FETO members in the Turkish Air Force. He remains on the run after having been released following his arrest.
The former professor returned to Turkey two days before the coup attempt. He had traveled abroad 109 times since 2002.
Oksuz allegedly traveled to U.S. on July 11 on same plane as Kemal Batmaz -- later identified as the second-in-command of the coup attempt.
They apparently returned to Turkey on July 13, again aboard the same plane. Footage appears to show that Batmaz was highly regarded among pro-coup forces at Akinci base, from where numerous jets that were active during the coup took off.
Oksuz is suspected of having transmitted Gulen's orders to launch the coup to soldiers on the night of the failed coup.
Crush them, kill them and go over them
Lt. Col. Levent Turkkan, former aide to Chief of General Staff Gen. Hulusi Akar, appears to have confessed to spying for FETO, namely on the previous military chief Gen. Necdet Ozel.
Similarly to numerous other suspected military FETO members, Turkkan said he was helped when he passed his military high school exam.
He said he learned about the coup attempt on July 14.
Chief of Staff Gen. Hulusi Akar said former Gen. Hakan Evrim, commander of Akinci air base, allegedly asked him to speak with Gulen, whom he described as an "opinion leader", while he was being held by pro-coup forces.
In ongoing investigations in Turkey’s central Konya province a suspect with the code name “Enes” spoke about the commands which the so-called “big brothers” within FETO -- trusted members who act as mentors to more junior people being brought into the organization – gave.
The suspect said a FETO member called him on the night of the attempted coup and said: “Whoever comes in your way, whoever wants to stop you, do not have mercy with them. Crush them, kill them and go over them.”
The suspect also said that various members of the terror organization also messaged him the same command.
Detained in Batman, Umit Eyvazoglu said that he had fulfilled the requests of the organization and that he was trying to break the resistance of the people who were rising against the coup.
Detained in northern province of Samsun, T.S., who was the responsible “big brother of commissars” said that through the ByLock messenger app, which is said to have been used by members of FETO during the coup attempt, members of the terrorist organization were ordered to support the coup attempt.
In his testimony, he said that the imam of the Samsun province commissars, who goes by the code name Yavuz and is a member of the organization, asked to support the soldiers who were attempting the coup.
20,000 soldiers are ready
Text messages between pro-coup officers appeared to reveal they had ordered the shooting of people resisting the July 15 coup attempt.
As part of the investigation into the thwarted coup attempt, the Istanbul Prosecutor's Office has compiled a series of WhatsApp messages between pro-coup officers, apparently sent on the evening of July 15.
One day before the coup attempt, the investigation appears to show that Col. Uzay Sahin wrote in a Whatsapp group that “20,000 soldiers are ready in Thrace”.
On the night of the coup attempt, Col. Uzay Sahin gave several commands in the WhatsApp group of the coup plotters.
Sahin was in touch with the general of the 54th mechanized infantry brigade, Hidayet Ari, the general of 55th mechanized infantry brigade Bekir Kocak, Maj. Mehmet Murat Celebioglu and Babaeski 1st army brigade commander Col. Gungor Gundogdu and ordered them to be ready for a meeting.
In another exchange that was revealed, Lt. Col. Ugur Coskun said officers and soldiers had been overrun by a group of protestors at the Istanbul Governorship building.
In a reply, Maj. Karabekir said: “Crush [them]. Burn [them]. No compromise.”
Another series of messages seem to attest that protestors were attacking pro-coup soldiers. Maj. Murat Yanik said he received an order from Ankara: "Open fire."
Shoot down instigators
Maj. Mehmet Murat Celebioglu said: "Sir, we received information that [there are] armed people. If people march towards us, we will open fire first in the air then at them."
Col. Sahin advised Celebioglu to shoot down leaders of protestors. "Shoot down instigators," wrote Sahin.
After it became clear that the attempt had been thwarted, the messages seemed to show a sense of disarray among the officers.
“Sir, we have been trying to survive. Do as you see fit,” said Maj. Mehmet Murat Celebioglu in an apparent message to someone asking for instructions.
Ismail Yigit, an alleged member of the Erdogan assassination team, asked his group before their mission: "Anybody not from Hizmet movement here?" Hizmet is another name for Gulen’s movement.
Yigit's statements were counted as evidence in court hearings.
Former gendarmerie Col. Arif Kalkan said that during a meeting of plotters he was told by Lt. Col. Mehmet Aydin the takeover had been ordered by Gulen.
Kalkan also apparently confessed that he had been close to the group since his military high school days.
Former Lt. Col. Fazil Ergun, who had allegedly been with the group since high school, also said the plot had been orchestrated by Gulen and orders passed to participants on July 12.
Ergun said he had met with coup-plotters in Tandogan district in Ankara on July 12 at 10 p.m. (1900GMT).
Footage at Staff College
Security camera footage from the War Academy in Istanbul appears to show pro-coup officers locking themselves in a meeting room from 9.04 p.m. (1804GMT) on July 14 until 12.30 a.m. on July 15 (2130GMT, July 14).
Brig. Gen. Fatih Celaleddin Sagir is another army general who allegedly admitted he was linked to FETO.
Commander of the 5th Infantry Training Brigade in the central Sivas province, his testimony shows he said he was introduced to FETO during his years at the Military Academy.
“I was in contact with them from 1988 to 1992. However, from 1992 until 2007, I was just a sympathizer,” he said.
Sagir was alleged to be promoted as a commander of martial law in case the coup attempt succeeded.
The first indication that pointed to FETO involvement was uncovered on the night of the attempt, when Istanbul's former Security Branch Manager Mithat Aynaci, was arrested after being caught in a tank dressed in military uniform.
Aynaci had been suspended from duty in November 2014 over suspected links to FETO. He was later dismissed.
Meanwhile, Lokman Kircili and Gursel Aktepe were arrested on their way to "take control" of the Security Headquarters' Intelligence Bureau in Ankara on the night of the coup.
Aktepe, who was arrested over his alleged connection to the coup attempt, said in his testimony that the Gulenist movement had given him 4.500 Turkish liras (around $1400) every month after he was dismissed from his position as Ankara deputy police chief last year.
He said he used to "receive money" from a person with the code name "Zubeyir", who works for Samanyolu College reportedly linked to FETO.
During a search of premises, police found one-U.S. dollar bills believed to have been sent by Gulen in order for followers to recognize each other.
You will be hanged at dawn
Many detained FETO suspects' dollar bills have been added to evidence by Turkish police who believe the serial-number letters on the banknotes are used as code within the organization.
Moreover, a prayer popular among Gulenists was found in the pocket of former air force Lt. Haldun Gulmez, who allegedly bombed President Recep Tayyip Erdogan’s hotel in Marmaris during the attempted coup.
Alleged FETO member, journalist Tuncay Opcin, tweeted on July 14: “You will be raided when you are on the bed and you will be hanged at dawn.”
In addition, Mustafa Unal, who was author at Gulen’s newspaper Zaman also shared a tweet saying: “You’ll see what happens”.
Former police officer and suspect Emre Uslu fled to the U.S due to charges on him and he never returned.
Uslu, on Twitter said he will return on July 16 after one of his followers asked him when he was going back to Turkey.
He is wanted in a parallel state inquiry presented to an Istanbul court.
Prison guards in Izmir also discovered a note written to Gulen’s nephew Mezher Gulen. "Brother Mezher, you said the thing was done. This attempt failed. I guess the guys were not organized well. What will happen now, will there be a new attempt? I hope they don’t cause us trouble in here. Burn this note in toilet after reading it."
Former Brig. Gen. Mehmet Partigoc, a signatory to the plotters' televised statement announced a military takeover, and wrote in a note to his family: "It was our duty to stop the rot in our country. If I had not done this, they would have imprisoned me for life anyway."
Wives of soldiers arrested in civil servant exam probe
Around a hundred wives of pro-coup officers and soldiers were also jailed after July 15 over cheating in a 2010 civil service exam.
Wives of soldiers who played an active role in the July 15 coup attempt were also arrested.
Also, in another example, a former professor's statements on a TV channel that is known to be close to Fetullah Gulen and his movement had drawn ire on social media.
Osman Ozsoy, in a live TV program that took place a month before the coup attempt, said he wished he had become a colonel instead of a professor.
"I wish I had become a colonel instead of a professor, I could've helped more during this process,” currently fugitive Ozsoy said.
“We won't say that this country's future is dark. It is simple to end all these processes. It is a simple thing. With the will of Allah, it will end within a short time. Turkey shall fear no danger," he said.
PKK's ties with FETO revealed
Police have also noticed that the terrorist group PKK received information from Turkish soldiers, who belong to the FETO terror organization in radio talks.
Turkey's General Command of Gendarmerie had issued a report revealing the links between the Fetullah Terrorist Organization, PKK and Daesh prior to and following the July 15 coup attempt, which left at least 249 people martyred and nearly 2,200 injured.
“An assessment of events, intelligence, intercepted radio conversations, and seized materials suggest that FETO members involved in the coup attempt could travel to regions with the help of Daesh and PKK members in order to avoid security forces,” the report said.
The FETO members then could launch -- together with other terrorist groups -- suicide bomb attacks, assassinations and armed attacks against Turkey, in an attempt to create chaos and internal conflict across the country, it added.
The attempt by sections of the Turkish military to overthrow the government began at around 10 p.m. local time (1900GMT) Friday and was thwarted by 8 p.m. Saturday.
A total of 249 people were martyred and more than 2,100 injured.
According to the government, the coup was organized by followers of U.S.-based Fetullah Gulen, who is accused of pursuing a long-running campaign to overthrow the government through supporters within the Turkish state, particularly the military, police and judiciary.