Noah Blaser and Aaron Stein

On October 10, twin explosions tore through a crowded peace rally in Turkey’s capital of Ankara, killing 102, injuring hundreds, and earning the tragic distinction of Turkey’s deadliest ever terror attack. For many, however, the bombing was hardly a surprise. Three previous, smaller-scale bombings had struck similar targets earlier that year, igniting ethnic conflict and bitter national divisions ahead of two consecutive parliamentary elections.

In recent days, Turkish media reports have defied a sweeping press ban over the attack, revealing critical details about the single network tied to all four bombings – as well the contours of wider network which took advantage of Turkey’s permissive border policy to move Turkish fighters to and from the Syrian conflict.

The culprits of all four attacks were members of a single cell of Islamic State (ISIS) from Adiyaman, a pious, Kurdish majority city of 220,000 in southeastern Turkey. While the group has been cast in Turkish media as an opaque network of ISIS-inspired youth, its key members spent time in northern Syria in 2013 and 2014, and were all recruited by a single individual after returning to Turkey. At its peak, the cell numbered at least 31 core members, including at least four foreign wives who had connected with the group in Syria, according to information collected by the two authors.

Repeated failures by Turkey’s police and national intelligence service to arrest the group’s key individuals enabled the Adiyaman cell to gather on a near daily basis and recruit more people. The group managed to make contact with older, more entrenched Al Qaeda linked Turkish networks that began sending fighters to the Syrian conflict in 2012. Members of the Adiyaman cell used this network to procure explosives, flee Turkey before major attacks, and to evade border controls while crossing back from Syria before three out of the four attacks.

Since it launched its first attack in 2014, the deadliness of the group has immeasurably grown. According to data from the International Crisis Group, the group killed 141 Turkish civilians, police and soldiers in 2015, nearly equaling the 158 security officials killed by the insurgent Kurdistan Workers’ Party (PKK) over the same period.

The bombers’ most devastating effect, however, is an unparalleled ability to widen Turkey’s bitter ethnic and political fault lines. Fighting Kurdish militias linked to the Kurdistan Workers Party (PKK) in northern Syria, the Islamic State targeted the country’s nationalist Kurdish movement in all four of its attacks on Turkish soil.

The group remains active. At least four of its members are now reportedly at large in Turkey, and police fear that they could carry out another attack in the near term. The media reports and leaked police testimony indicate that the Adiyaman cell operated unmolested for close to a year between 2014 and 2015, before the first wave of police raids against the Islamic State prompted some members to flee to Syria around March 2015. A large number of the Adiyaman cell’s member crossed back to Syria around this time, with many fighting against the Syrian Kurds during the waning days of the battle for Tel Abyad.

After the Islamic State’s defeat in late June, a small group of Adiyaman cell members appear to have been ordered to return to Turkey to continue the war against the PYD inside Turkey. To facilitate these attacks, the Adiyaman cell relied on the Islamic State’s network spanning from Kilis to Gaziantep. These deep networks pose a longer term threat to Turkey and appear to be the target of a recent wave of arrests that have taken place after the Ankara bombing.

However, a recent police operation in Diyarbakir against another group of Islamic State supporters suggests that Ankara faces a longer term threat from radicalized individuals operating inside of Turkey. Thus, while Turkey has recently increased its anti-ISIS activities, its previous neglect may have allowed for the group to gain strength. Data from the International Crisis Group shows that Turkey formally arrested at least 128 individuals and has detained at least 400 on charges of ISIS Islamic State membership in 2015. According to sources in the Foreign Ministry, Turkey has denied entry or deported approximately 3200 foreign nationals seeking to travel to Syria since April 2014. Nevertheless, the Islamic State is reported to have approximately 20,000 foreign fighters, the vast majority of whom passed through Turkey.

In July, Turkish authorities arrested Halis Bayancuk, a cleric widely regarded as Turkey’s leading pro-Islamic State pundit. Bayancuk’s activities until that date, however, are grim testament to the freedom jihadist voices long enjoyed in Turkey: In October 2014, he was inexplicably released from jail halfway through an Al Qaeda-related prison sentence. In June, Bayancuk had felt free enough to complain in an online lecture that his followers were texting him too many photos of victims they had beheaded in Syria.

Along Turkey’s border with Syria, Islamic State still manages to smuggle goods to Syria and ultimately Iraq, relying on middlemen who are often based in Turkey. As late as October 2015, the Adiyaman members were able to take advantage of those weaknesses, crossing the Syrian-Turkish border, eluding police, and carrying out the most devastating bombing in Turkish history.

The Cell

Adiyaman Cell Name Alias Role Mustafa Dokumaci Leader of the cell Ahmet Korkmaz Spiritual Emir and recruiter of the Adiyaman cell’s core members. Presumed to have fled to Syria. Unkown Haci Kasap Named in testimony by captured cell members, Haci Kasap had an unknown leadership role. Ibrahim (No last name) Met with cell members after Ahmet Korkmaz fled to Syria, arranged safe houses and border crossings Omer Deniz Dundar Emre Kaya Spent time fighting against Kurdish militias in Syria in 2014 and 2015. Tea house attendee. Reportedly at large. Listed on Ankara’s ‘red list’ of most-wanted individuals. Merve Dundar German national. Married Omer Deniz Dundar in Syria, and a became teahouse attendee. Reportedly at large. Listed on Ankara’s ‘red list’ of most-wanted individuals. Yunus Emre Alagoz Manager of the Islam Tea House and core Adiyaman cell member. One of two Ankara suicide bombers Seyh Adburrahman Alagoz Assisted his brother Yunus if managing the Islam Tea House. Suruc suicide bomber. Orhan Gonder Diyarbakir bomber and core Adiyaman cell member. Arrested in Gaziantep after the Diyarbakir attack. Kasim Dere Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Mehmet Mustafa Cevik Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Salih Kucuktas Attended sermons and meetings at Adiyaman teahouse Mahmut Gazi Dundar Traveled to Syria in 2014. Adiyaman teahouse regular. Listed on Ankara’s ‘red list’ of most-wanted individuals. Muhammet Zana Alkan Murat Ozalp Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Mehmet Tasar Attended sermons and meetings at Adiyaman teahouse. Helped radicalize his wife, Demet. Demet Tasar Attended sermons and meetings at Adiyaman teahouse. Married to Mehmet. Radicalized after her husband began to attend the tea house. Memet Isbar Attended sermons and meetings at Adiyaman teahouse. Huseyin Mustafa Peri Spent time in Gungoren, Istanbul. Close friends with Mahmut Gazi Tatar. In PYD custody. Linked to HISADER, whose lawyer, Osman, died fighting with Nusra in 2013. Mehmet Isik Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Ersel Ocak Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Aysenur Inci Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Utkar Mammadova Tea house attendee. Azeri national. Whereabouts unknown. Recep Yaman Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Haci Yusuf Kizilbay Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Kadir Gozukara Attended sermons and meetings at Adiyaman teahouse. Listed on Ankara’s ‘red list’ of most-wanted individuals. Fatma Kendah Tea house attendee. Possible foreign wife of Adiyaman cell member. Walentina Slobodjanjuk Yildiz Bozkurt Reportedly married Mahmut Gazi Dundar in Syria. Reportedly at large. Yakup Aktulum Tea house attendee. First visited Syria in 2013 with IHH. Fought with Ahrar al Sham. Mahmut Gazi Tatar Tea house attendee. Friends with Huseyin Peri. In PYD custody

The picture is incomplete, but it appears that the Adiyaman group was built like a typical Islamic State cell: In addition to the group’s leader, Mustafa Dokumaci, it also had a spiritual Emir, identified in police reports as Ahmet Korkmaz.

A third man, known as Haci Kasap also had a leadership role, but has reportedly been arrested. Korkmaz reportedly met with at least four members of the group at his house in Adiyaman’s Bachelievler district, where the group also maintained a tea house and prayer room.

From its beginnings in 2013 – when Turkish and international media first flagged jihadist activity in Adiyaman – the cell expanded in size as its members moved freely between Syria, Gaziantep and Adiyaman. Some members traveled to Syria in the service of Islamist NGOs, others as members of the Islamic State. Future bombers Seyh Adburrahman Alagoz, Yunus Emre Alagoz and Orhan Gonder reportedly traveled to Syria in 2014, as did long-time cell members Omer Deniz Dundar, Mahmut Gazi Dundar, Huseyin Peri and Mahmut Gazi Tatar. An eighth man, Yakup Aktulum, first travelled to Aleppo in 2013 with the Humanitarian Aid Foundation (IHH), an Islamist NGO that controls much of the Turkish aid delivered to Syria, according to an interview with his father in the Turkish daily Radikal. Aktulum stayed in Syria for an additional four months, reportedly joining the Salafi Ahrar al Sham, a group with close links to the Turkish government and who has received aid from IHH.

Questioned and released by Turkish authorities when he returned to Adyaman with a severely injured leg in 2014, police reports cited in Radikal indicate Aktulum confessed that he was a frequent visitor of the Adiyaman teahouse. He remains in Adiyaman and is undergoing treatment for post-traumatic stress disorder, according to his father.

The cell’s recruitment efforts were not confined to Adiyaman’s city limits. Korkmaz recruited at least one of the group’s members, Mahmut Gazi Tatar, at a refugee camp on the outskirts of Adiyaman in 2014. Tatar soon began to attend religion courses at his home.

Detained by Syrian Kurdish militants in 2015, Tatar explained in an interrogation video posted by his captors on Youtube that four other men – Yusuf, Ibrahim, Mustafa, and Heymen – also attended lectures at Kormaz’s home. While Tatar did not mention any of those mens’ last names, Mustafa likely refers to Mustafa Dokumaci, the leader of the Adiyaman group. The other three remain unaccounted for.

In 2014, Tatar befriended Adiyaman native Mustafa Peri, who was working at a bakery in the Istanbul neighborhood of Gungoren, Sevik Dinc, a HaberTurk reporter who visited Adiyaman in early July, told one of this report’s authors. Like Tatar, Peri was taken prisoner while fighting Kurdish forces in Syria, and recently detailed the circumstances of his recruitment in a lengthy video the PYD has posted on YouTube .

In 2014, Peri came into contact with HISADER, a local Islamist NGO that had opened an office and prayer room above the bakery where he worked in Gungoren. The NGO’s founder, Volkan Saglam, is linked to Jabhat al Nusra through the organization’s lawyer, Sinan Karahan, whose brother, Osman, was killed fighting with Nusra near Aleppo in 2013. In a photo posted in June, 2014 on Twitter, Saglam sits beside Musa Hoca, a close affiliate of Halis Bayuncuk. Known by the alias Ebu Hanzala and deemed Turkey’s most prominent pro-Islamic State preacher, Bayuncuk was arrested along with Musa Hoca during a police raid in Istanbul in July 2014. The Turkish government shut Hisader down in July 2014 after local residents complained that it was recruiting locals to join the Islamic State.

In the spring of 2015, Turkish authorities launched a nationwide wave of anti-Islamic State arrests, prompting the Adiyaman cell to slowly retreat to Syria and safe houses in Gaziantep. It is unclear when Dokumaci left Turkey, but he now reportedly resides in Raqqa, the Islamic State’s de-facto capital. In his interrogation video, Mahmut Gazi Tatar indicates that Ahmet Korkmaz traveled to Syria in March, entrusting a figure known as “Ibrahim” continue the Adiyaman cell’s spiritual training.

In their video interrogations, Peri and Tatar stated that they worked with “Ibrahim” to arrange their own safe passage to Syria. It is unclear if Tatar and Huseyin are referring to the same person. “Ibrahim” is a popular nom de guerre that Turkish Islamic State members have adopted, perhaps in homage to the so-called Caliph Ibrahim, Abu Bakr al Baghdadi.

At least 60 Adiyaman residents have joined various jihadist groups in Syria since 2011, according to Turkish authorities. At least five men from Adiyaman have been killed near Aleppo between 2013 and 2015: Mehmed Ali Özdemir; Abdulkadir Adiymanli; Ferhat Avci; Mehmet Samsama; Ismail Samsama. Mehmed Ali was reportedly a veteran of Afghan jihad, where he fought against U.S. forces for four years. Abdulkadir appears to have been a leader of an al Qaeda unit near Aleppo, and was killed in 2013.

Islamic State Strikes in Turkey

While domestic pressure on the Adiyaman cell grew in early 2015, numerous Adiyaman cell members speaking to police indicate that the defeat of the Islamic State in Tel Abyad prompted the group to take action. After defeating the Islamic State during the battle for Kobane in October 2014, the Democratic Union Party’s (PYD) militia, the YPG, began to steadily take territory from the Islamic State along the Syrian-Turkish border. By June 2015, YPG forces had surrounded the Islamic State-controlled town of Tel Abyad, the key overland route from Turkey to Raqqa. The town fell in June. Of the Adiyaman group, Huseyin Peri, Mahmut Gazi Tatar, Seyh Abdurrahman and Yunus Emre Alagoz, and Orhan Gonder fought in the battle. Huseyin and Tatar were taken prisoner by the PYD.

In May, as Kurds slowly advanced on Islamic State positions in northern Syria, simultaneous blasts rocked two offices of the Kurdish-majority Democratic Peoples’ Party (HDP) in the southern Turkish cities of Adana and Mersin, wounding three. Police declared that the attack on the HDP – which cooperates closely with the PYD and champions its cause in Turkey – was carried out by Savas Yildiz, a 32-year old Van native who had been briefly detained on suspected links to Syrian jihadist groups in early 2014.

Turkey’s first Islamic State-linked bombing would not be recognized as such, however, with Prime Minister Ahmet Davutoglu implying that the attack had been carried out by a Marxist group, rather than the Islamic State, in the run-up to June parliamentary elections. Yildiz had indeed been detained for militant Marxist links in 2007, but his conversion to the Islamic State was real, numbering among the many radical, seemingly implausible paths to jihadist recruitment taken by some Turkish citizens.

Eluding Turkish security forces after the Adana and Mersin bombings, Yildiz is believed to have fled to Syria, where he likely made contact with members of the Adiyaman cell. On October 24, Turkish police listed Yildiz among four bombers-at-large in Turkey.

Diyarbakir Attack: Orhan Gonder

The second Islamic State-linked attack took place on the eve of June 7 election at a HDP campaign rally in the Kurdish majority city of Diyarbakir. Gonder detonated two crude explosive devices in the crowded rally, killing four and wounding more than a hundred people.

Gonder later told police after his arrest that he was drawn to the Islamic State in October 2014, after members of the Kurdistan Workers’ Party’s (PKK) youth group, the YDG-H, attacked Kurdish Salafists affiliated with group Huda Par. The riots began after the HDP’s co-chair, Selahattin Demirtas called on the party’s supporters to protest the Turkish government’s inaction during the Islamic State’s siege of the PYD in Kobane in early October 2014.

The clashes resulted in some 50 deaths, the bulk of which were Huda Par members. Gonder’s father told the Wall Street Journal that Orhan’s behavior changed dramatically and that he began to frequent the tea house and pray alongside other members of the Adiyaman cell while studying for the University entrance exam in 2014. The growing popularity of the tea house prompted more than a dozen families to complain to the authorities, but little was done to shut it down. The authorities did question Gonder in June 2014, but after denying that he had any intention of travelling to Syria, he was released.

Gonder then reportedly travelled to Syria with the Alagoz brothers in October, where they were eventually tracked to Tel Abyad. Along with Seyh Aburrahman, Gonder reportedly fought with the Islamic State in Tel Abyad against advancing Kurdish forces. By late June 2015, the Islamic State only retained control over two official border crossings: Elbeyli and Karkamis. Gonder probably crossed back into Turkey near Elbeyli, before travelling to Gaziantep.

In police testimony described in the Turkish daily Sabah, Gonder indicated that a third individual, known only as “Serdar,” arranged for him to return to meet an unidentified fourth man in Gaziantep two days before the June 7 attack. According to the same leaked police testimony, that individual gave Gonder three prepaid mobile phones and instructed him to travel to Diyarbakir by bus. Gonder’s description of Serdar closely matches that of Ilhami Bali, who police suspect of playing a central role in organizing the October 10 Ankara attack.

According to police, the 28-year old native of Reyhanli, a Turkish border town in the province of Hatay, became a key smuggler for the Islamic State after finishing prison sentence on Al Qaeda charges in 2012. Bali’s name is included on Ankara’s “red list,” a lineup of Ankara’s most wanted criminals that includes top PKK lieutenants and leaders of various extreme leftist groups. He remains at large and is presumably in Syria.

The police briefly detained Gonder upon his arrival at a hotel in Diyarbakir for dodging his military service. However, the arresting officer did not know that the national intelligence service had flagged him as a potential suicide bomber and member of a Jihadi group. After the attack Gonder returned to Gaziantep, but the police arrested him before he could cross back into Syria.

Suruc attack

In July 2015, three separate events preceded the Islamic State’s third and then-deadliest attack on Turkish soil.

On July 1, YPG forces captured the border town of Tel Abyad, choking a critical supply route to the Islamic State’s capital of Raqqa. On July 10, Turkey launched its largest-ever wave of jihadist arrests, detaining over 100 suspects nationwide and formally arrested leading pro-Islamic State cleric Murat Gezenler, a powerful Konya based Salafi cleric with links to Al Qaeda. Police also arrested Abdulkadir Polat, the head editor of Turkey’s most active pro-Islamic State websites, and Cumali Kurt, a close confidante of Halis Bayuncak.

Earlier that week, Turkish and American officials had reportedly reached a tentative agreement to open Incirlik Air Force base to aircraft bombing Islamic State positions in Syria and Iraq, according to Turkish journalist Amberin Zaman. While the plan still required sign off from President Recep Tayyip Erdogan, Turkish security officials began to leak news of the agreement. To finalize the arrangement, the two sides scheduled a call between Erdogan and U.S. President Barack Obama for July 22, according to a US official speaking to one of the authors.

On July 20, 20-year old Seyh Abdurrahman Alagoz detonated a suicide vest at a gathering of the Socialist Party of the Oppressed (ESP) in the Turkish border town of Suruc, killing 33 mostly college-age activists. Like previous bombings, the attack targeted a group linked to the HDP. Figen Yuksekdag, the party’s co-chair, had been president of the ESP before the HDP’s creation, and the group had intended to deliver toys, books and foodstuffs to the Kurdish city of Kobane in neighboring Syria. The ESP’s sister organization, the Marxist Leninst Communist Party (MLKP) has sent fighters to fight alongside the YPG against the Islamic State, purportedly as part of a larger project to create a communist state.

A core member of the tea house, Alagoz traveled to Syria with his brother, Yunus Emre Alagoz, in 2013, and was questioned by authorities after returning to Adiyaman the following year, according to Ayhan Bilgen, an HDP deputy. Citing police sources, Turkish daily Radikal reported that Alagoz denied any personal links to the Islamic State, but confessed that his older brother had traveled to Afghanistan between 2009 and 2010. Authorities wiretapped Alagoz after he fled to Syria with Orhan Gonder in late 2014, but neither brother was arrested.

Though the Islamic State has made no claims of responsibility for the Suruc attack, police later determined that Alagoz’s suicide vest was identical to 33 explosive vests confiscated during a raid in Gaziantep in October 2014, an unnamed security source told CNN Turk.

If the group hoped its silence would feed convictions of distrust and division in Turkey, it was an unqualified success. On June 22, PKK militants – acting on the belief that Turkish security forces had covertly aided Alagoz – killed two police officers in the southern city of Sanliurfa. That reprisal derailed a 2-year ceasefire between Ankara and Kurdish insurgents, prompting the Turkish air force to begin airstrikes in Iraqi Kurdistan and southeastern Turkey.

Overshadowed by its crackdown on Kurdish militants and political groups, Ankara also deepened its commitments to fighting the Islamic State. On July 23, one Turkish officer was killed during a border skirmish with militants in ISIS-held Syria, prompting Turkish artillery and airstrikes on Islamic State targets. Later that day, Ankara announced that it had finalized a deal to allow U.S. warplanes to strike targets from Incirlik airbase.

Ankara Attack

On the morning of October 10, two men stepped out of a taxi at the entrance of Ankara’s central train station, where thousands of activists had gathered for a day-long peace march. Weaving among a crowd of demonstrators from the HDP and its leftist sister parties ESP, MLKP and Socialist Party of Refoundation (SYKP), the two men detonated their vests in near-simultaneous explosions, killing 102 people and injuring hundreds more.

One bomber would later be identified by Turkish police as Yunus Emre Alagoz, the manager of the Adiyman tea house and brother of the Suruc bomber, Seyh Abdurrahman Alagoz. The identity of the second bomber, believed to be a foreign national, remains unknown.

The Ankara bombing was carefully planned, and its execution relied on the use of safe houses in Gaziantep, continued access to Turkish soil from ISIS-held Syria, and detailed organization by several Turkish nationals.

Days before the attack, the two bombers crossed over the border from ISIS-held Syria, likely passing near the town of Elbeyli in Kilis province, the last direct point of entry from Islamic State-held Syria into Turkey.

According to a police report leaked by the mainstream Fox TV, police had been notified about their passage into Turkey, though they later lost track of the attackers. Security officials had also vowed to clamp down on the border earlier in the year, but cross-border smuggling has continued, while in September, one Turkish soldier was killed and another kidnapped in clashes with smugglers near Elbeyli. The missing soldier is presumed to be in ISIS hands.

On October 9, Alagoz and his unidentified companion reportedly assembled their suicide vests in a safe house in Gaziantep. They were joined by Halil İbrahim Durgun, who had helped facilitate their border crossing, and Yakup Sahin, a local baker. Arrested after the attack, Sahin detailed the contours of the plan in testimony that was widely published by Turkish media. According to Sahin, the three men were subordinates of Yunus Durmaz, who used the alias “Ebu Ali” and owned several warehouses in Gaziantep.

Few clues exist about Durmaz’s origins. Turkish media dubbed Durmaz the “Emir of Gaziantep,” while in 2015, a report from Kilis by the Turkish daily Birgun claimed that an “Ebu Ali” tightly controlled smuggling efforts in Kilis. Murkier still is the identity of a man identified by anonmyous police sources as “Cemil,” who is believed to have planned the attack inside of Syria, instructing the bombers to target the HDP’s main headquarters in Ankara and assassinate HDP co-chair Figen Yuksekdag.

On October 9, the two bombers travelled to Ankara in a car driven by Durgun. Yakup Sahin rode ahead in an advance car, scouting for police checkpoints on the highway, according to his police confession. Three weeks before their departure, police across Turkey had been warned by the national intelligence service of a looming ISIS attack. At a checkpoint on the outskirts of Ankara, police stopped and questioned the drivers of both cars, but quickly waved the vehicles through, according to the Sahin testimony cited in Haberturk. When Alagoz and the second, unidentified bomber arrived in Ankara, they stepped out of Durgun’s vehicle and hailed a taxi. Learning of the rally on the way to the HDP headquarters, the bombers reportedly asked the driver to stop near the entrance of Ankara’s main train station, where they then detonated their suicide vests.

In the aftermath of the bombing, Turkish Prime Minister Ahmet Davutoglu implausibly speculated that ISIS, the PKK and Syrian intelligence had coordinated the attack, while an Ankara court on October 14 ordered a sweeping media ban on coverage of the bombing. Still, all evidence has firmly pointed to the Islamic State. Speaking two days after the attack, Deputy Prime Minister Numan Kurtulmus indicated that the explosives used were similar to the device Seyh Abdurrahman used in July, further linking the Ankara attack and Suruc bombing with the October 2014 raid the led to the confiscation of 33 suicide vests in Gaziantep.

On October 20, Turkish police raided a warehouse in Gaziantep, reportedly after Yakup Sahin told his police interrogators that Durmaz maintained warehouses in the city to store munitions and assemble suicide vests. The raid netted bomb making materials, including explosives identical to those used in the Suruc and Ankara suicide vests. Turkish police believe Durmaz left Gaziantep the night before the Ankara attack, crossing the border near Elbeyli with Halil Ibrahim Durgun’s assistance.

The warehouse is one mile from Gaziantep’s Savcili neighborhood where, less than one week before the Ankara bombing, Turkish police raided a facility manufacturing the Islamic State’s gold currency, the gold dinar. The warehouse is also less than 3 miles from an alleged Islamic State inspired Kuran course and meeting house.

Significant loose ends remain. When police arrested Sahin, they also arrested his nephew, Hakan Sahin, who had checked into the the Yildiz hotel, located in Ankara’s Hacibayram neighborhood, two days before the attack.

ISIS recruiters have have long recruited men from the low-income district, while police detained 15 ISIS suspects in Hacibayram in July 2015. Police later released all 15 suspects. Though Hakan Sahin may have acted as a scout for the attack, his exact role remains unclear.

Since the attack, police have issued arrest warrants for at least 14 individuals, including Yunus Durmaz and Deniz Buyukcelebi, an Islamic State member who brought the bombers’ suicide vests from Syria to Gaziantep. Authorities have increasingly suspected that Ilhami Bali, a Turkish-born ISIS member known to coordinate smuggling along Turkey’s border with IS-held Syria, may have also played a role in organizing the attack. Descriptions of Bali closely match that of an individual who allegedly assisted Orhan Gonder, the Diyarbakir bomber, in carrying out his attack in June.

According to Turkish police, at least four potential suicide bombers remain on the loose in Turkey, including Adiyaman cell members Muhammet Zana Alkan and Omer Deniz Dundar, Dundar’s wife, Walentina Slobodjanjuk, and Savas Yildiz, the Adana and Mersin Bomber.

Slobodjanjuk and Merve Dundar are both from Mönchengladbach, a city with a reputation as a Salafist stronghold. The Turkish police reportedly contacted their German counterparts after the Suruc attack to inquire about Slobodjanjuk and Merve, but by that point they may have already fled to Syria with Omer and Muhammet.

The Threat

On Oct 26, two Turkish police were killed while attempting to raid an ISIS safe house in the majority Kurdish city of Diyarbakir. The raid triggered a bloody, hours-long gun battle, saw one jihadist detonate a suicide vest, and ended with the death of 7 militants and capture of 12 others.

While the shootout underscored Ankara’s growing willingness to confront ISIS, the slain fighters’ origins show that security lapses have nurtured Islamic State cells in other cities besides Adiyaman.

Five of the fighters were from the rural, southeastern town of Bingol, where at least 45 families complained to authorities in 2014 and 2015 about children who joined jihadist causes in Syria. The city’s link to jihadist movements stretches back to the 1990s, when pro-Al Qaeda networks funneled recruits to Pakistan and Afghanistan . In 2003, two men from the town participated in a series of suicide attacks in Istanbul that killed 57 people. The brother of one of those bombers died in Aleppo fighting with Jabhat al Nusra in 2012. Despite Bingol’s troubling history, police have made just one Islamic State-linked arrest in Bingol in 2015.

The Islamic State recruits from a wide base in Turkey. Orhan Gonder, the Diyarbakir bomber, was both a Kurd and Bektaşi Alevi. In Turkey, recovering drug addicts and activist college students have joined the group’s ranks in Syria. Though the motivations of ISIS recruits in Turkey remain varied and complex, limiting the group’s reach is a different matter. In Adiyaman, one man was involved in radicalizing several youth that would kill more than 100 people. The parents of his followers had repeatedly described his activities and whereabouts to police.

Meanwhile, along the Turkish-Syrian border, the illegal flow of goods and people continues, despite ISIS complaints of stiffened security measures. The Adiyaman cell flourished thanks to those open borders. Members hardened their newfound convictions in Syria, whether in the service of Islamist NGOs or by fighting on the civil war’s frontline. Cell members freely returned to Adiyaman and recruited new members. Most had returned to Syria by 2015, when they contacted the ISIS facilitators who made their attacks possible.

In the aftermath of the Ankara bombing, Turkish officials have dubiously insisted that ISIS was only one registered terror group of many involved in the Ankara attack. Every sign however, points to ISIS. Moreover, its bombings in Turkey seem to have been planned by leaders in Syria, suggesting that the group has settled on a strategy of striking Kurdish activists to sabotage Turkey’s political and ethnic cohesion.

Turkey’s government must urgently hasten its crackdown on the group. After years of unhindered ISIS recruitment and network-building in Turkey, the confrontation is sure to be a long and difficult one.

Noah Blaser is an independent journalist based in Istanbul since 2011.

Aaron Stein is a Nonresident Fellow with the Rafik Hariri Center for the Middle East, a Doctoral Fellow at the Geneva Center for Security Policy, and an Associate Fellow at the Royal United Services Institute in London.