“We have a Palestinian who wants to talk. Do you want to speak with him?” 

The Iraqi Kurdish prison guard’s words made me sit bolt upright. My colleague and I glanced at one another, our faces contorted with curiosity.

We had travelled to Iraqi Kurdistan as much of the world’s gaze was drawn to the crisis surrounding the US troop withdrawal from northern Syria, Turkey’s ensuing offensive against the Syrian Kurds and fears that thousands of ISIS militants in Kurdish prisons could escape amid the fighting.

Less attention is being paid to those in the custody of the Iraqi Kurds, who find themselves on a more stable footing in their well-protected, semi-autonomous region of northern Iraq. We hoped to find a case worthy of the public’s interest, one unique from the dozens of prisoner interviews conducted in recent years.

The next line uttered by the guard would deliver that: “He has an Israeli passport.”

The answer to his question was an easy one.

Israeli Arabs who took flight to join ISIS are a rarity. More militants from each of Trinidad, Switzerland and Finland fought under the group’s black flag than Israeli Arabs. Only 60 have been recorded as travelling to Iraq and Syria, and none have ever spoken to an English-language publication.

Kurdish security had whisked us at short notice to a sterile counter-terrorism centre a 20-minute drive outside Sulaymaniyah – Iraqi Kurdistan’s second city – at the direction of Lahur Talabany, the region’s counter-terror czar. As the head of the Zanyari spy agency, he is one of the most powerful intelligence figures in the fight against ISIS.

His agency's base in Sulaymaniyah is a critical hub in that battle. It possesses an "advanced intelligence department" with "important investigative papers" and "very important documents" relating to ISIS and their captured fighters, according to Hisham Al Hashimi, an Iraqi researcher and security adviser to the Iraqi government. It also holds some of the group’s die-hard fighters, including a one-time member of its hostage-negotiation team.

As we sat in the facility's office, a large image of Jalal Talabani, the first Kurdish president of Iraq – known as Mam Jalal, or uncle – watched over us. 

An armed special-forces commando approached the door, guiding a lumbering figure who towered over him. The soldier slid a greyish-brown face cover off the detainee's head.

The smirking, barefooted man under the cloth was Mohammed Khalid, a weary and dishevelled 28-year-old who prison staff say is one of the most dangerous men in their custody, a fighter who has spent 21 months in solitary confinement without trial. He is handcuffed and blindfolded as he goes from room to room so he cannot learn the centre’s layout.

He was – at least at one time – a holder of Israeli citizenship, coming from the country’s Arab-majority Northern Triangle area, where residents are mostly Palestinian. Now, his citizenship status is unknown.

When Jordan, one of only two Arab states to have diplomatic ties with Israel, tried to return him to his home country sometime between his capture in eastern Syria in December 2017 and his arrival in Iraqi Kurdistan in February last year, the offer was refused, according to an Iraqi official. Israel’s hard-right government has tried to block the repatriation of the hardened Arab extremists that left its territory. It has moved to revoke the citizenship of at least 20 Israeli Arab fighters since 2017, in one case distributing a news release about the bid to strip a militant of his passport and identifying him in the process. 

Yet, in Khalid’s case, his government refuses to acknowledge his existence as an Israeli. The Israeli Interior Ministry said it does not have any information about a Mohammed Khalid. It is unknown if Khalid even retains his Israeli citizenship.

“We have nothing about such a person. We are not familiar with the case,” a ministry official told The National.

But all of the evidence points to the Israelis knowing about Khalid. Iraqi Kurdish security, Khalid’s family and their lawyer all confirmed his name and nationality to The National. His Israeli university confirmed his attendance, dispelling the official’s suggestion that he could have provided a false identity upon capture. The National saw his Israeli ID card, provided by his family, and is publishing it here with his face and personal details hidden.

The Israeli Interior Ministry official refused to answer repeated follow-up questions, saying the information about Khalid had been passed on to the security services. Neither the Shin Bet - Israel's domestic spy agency - nor the Israeli Prime Minister’s Office responded to requests for comment. An Israeli Foreign Ministry spokesperson simply replied: "No comment."

Scooped up in an American special-forces raid in December 2017 between the Iraqi and Syrian border towns of Qaim and Al Bukamal before being passed around by four regional players - the United States, Jordan, the Iraqi government and the Iraqi Kurds – Khalid is like most captured ISIS fighters: unwanted. The assumed reason he was moved around is that their different intelligence services believed they could glean new information from him.

Asked about Khalid’s case, the US-led coalition referred The National to the Israeli authorities. A Jordanian government spokesman said he had no knowledge of Khalid’s case. The Jordanian and Iraqi interior ministries did not respond to requests for comment. 

The Israeli denial of Khalid’s case, his nationality, even his very existence as a citizen, contradicts his story that the Israeli security apparatus not only knows about him, but approached him at least twice before he left for Syria. It also goes against the Iraqi claim that Israel refused to take him back after his capture, as well as his family’s detailing of interrogations by Israeli airport officials about Khalid as they travelled out of the country.

This is the unrepentant militant’s story, garnered from the first English-language interview with a captured Israeli Arab ISIS fighter and interviews with his relatives after The National tracked them down in northern Israel's Arab heartland. They detail his path to radicalisation, his journey into the ranks of the world’s most feared terrorist group, his family’s anguish and his country’s total abandonment of him.

It is a case that terrorism experts say appears to have set a new precedent for dealing with foreign fighters considered traitors to their homeland, and one that a United Nations rapporteur says Israel, like all countries, has an obligation to resolve in cases such as these.

In August 2013, the Khalid family travelled with close friends to Taba, the small Egyptian town on the northern tip of the Gulf of Aqaba. On the other side of the border is their home country: Israel. Mohammed Khalid stayed behind. His reason: he did not want to see women on the beach.

Mousa and Hanan – Khalid’s parents – took their daughter, Tala, and son, Omar (whose names have been changed for security reasons), for a week’s summer holiday away from Umm Al Fahm, a northern Israeli city of 55,000 people, most of them Arab. The family’s trip would be cut short by four days.

Forty-eight hours of calls to Khalid, their first-born child who had stopped travelling abroad with them after high school, went unanswered. He had gone missing. Mousa asked Jaber, Khalid's uncle, to break into the house. Inside, Jaber would find blankets and pillows used by two guests. Near them were plane tickets and planning notes.

Mousa immediately called the Israeli police to report the 23-year-old’s disappearance, handing them his son’s phone and his laptop. It was too late. Khalid had checked into Ben Gurion Airport in Tel Aviv and left for Turkey. 

The tickets said he was heading for the southern Turkish city of Adana. The Israeli authorities told the family there was nothing they could do because Khalid was an adult. Two days later, Jaber travelled to Adana in a failed bid to find his nephew. The planning notes found at the house left a clue about another planned destination, Syria, but offered no specifics.

Two months later, in October, a private number appeared on Hanan’s phone. It was her son. She, along with Mousa and Tala – one year younger than Khalid – demanded that he return home. The brother, Omar, five years younger, was not at home. Mohammed refused but gave no reason why. The call lasted just five minutes and it would be the final time that an angry Mousa would speak to his son.

What followed were random phone calls to Hanan at intermittent periods for the next three years. Khalid would ask about home, his family and friends, once even complaining about changes they made to his old bedroom. The family say they never knew where he was in Syria; they did not want to know more about his life there.

Israeli police told them to drop the missing-persons case as he was in contact. The Israeli security services did not follow up with them, the family say.

In one call, Khalid threatened to cut contact with his mother if she repeated her demand that he come back to Israel. She stopped crying and begging on the calls for fear that they would stop, Tala said. But they would become less frequent anyway, until Khalid ended all contact with his family in late 2016 for reasons unknown.

For the next three years, Hanan would watch the news for any sign of her son. Khalid’s father, however, stopped watching or reading the news. Most of his family presumed Mohammed dead because of the lack of information about him. That is until November 20 this year, when The National passed an image of Khalid, taken in the Iraqi Kurdish prison, to Samir Mahamid, the mayor of Umm Al Fahm, whose number was retrieved from an Israeli Arab politician.

“I do not know who you are talking about,” he said.

But hours later, a WhatsApp message in Arabic appeared from an unrecognised Israeli number. It was from Mousa, who is Mr Mahamid’s doctor. “I am the father of the young man,” Mousa said, re-sending the same image of Khalid that had been sent to the mayor.

“How can you help us with some information about him? Please,” he wrote.

Mousa confirmed Khalid's date of birth and his name and sent a photo of his son in Israel to confirm that he was indeed his father.

The mayor had a flash of memory, recalling Khalid's case after three years despite no new information, and had contacted Mousa straight away.

“How did he get to Iraq?” he asked, adding that he thought his son had been killed.

After receiving the image of a gaunt version of his son in an Iraqi Kurdish prison, Mousa immediately left work and went home. He told his wife to sit down and showed her the picture. “I felt confused,” he said.

He then got to work with his lawyer, Hussein Abu Hussein, to think of ways to bring Khalid home. 

“He is not an enemy of Israel, and he did not do anything wrong to Israel,” he said.

When Tala came home later that day, Mousa sat her down too. She did not recognise her older brother. “He was much skinnier. Then my Dad explained the situation,” she said.

“I was relieved that he is alive.”

As Khalid sat down in the prison office chair at the beginning of a 50-minute interview, a fly crawled across his left hand, which was now freed from the cuffs. He beat it away and struck a nonchalant posture, like a schoolboy who had been told off but didn’t care. He asked that his face not be shown in any published images or video footage.

Wearing a navy jumper and baggy grey trousers, Khalid slouched with his head resting on his closed right hand and the other on his hip. It never left his body. At times his arms stayed tight to his torso, as if for comfort. He barely moved when he spoke, except for his rib-cage, which expanded and contracted with heavy breaths. 

Why he agreed to speak is unclear. Moroccan and Jordanian fighters had refused an interview just minutes before. Maybe he had been offered perks by his guards – the initial offer of an interview was made by them in his cell. Perhaps he longed for a shred of human interaction.

But he was eager to detail his path from Israel's Arab north to the ISIS front lines in Syria. 

Khalid’s story is a familiar tale of radicalisation: a lost soul who longed for something to fill the void, one whose life took a specific series of turns on to the wrong path, which in this case led to devotion to an extreme form of religion and an urge to fight in its name. This devotion would take him from the streets of his rundown, crime-ridden city, to the battlefield in Syria.

He was raised by two doctors in a middle-class Arab household. His father is a communist, a worldview far removed from the ideology Khalid would adopt. His younger brother and sister remain at home.

In his teens, Khalid was fond of drawing portraits. He loved animals, singing and bowling, which he would play competitively with his father, who participated in the senior leagues, his sister recalls.

“He is still the nicest person I’ve ever met,” Tala said in a Skype call with her father from the family home. She remembered how Khalid once offered her a ride in his car to the bus station, where she would travel on to university in Jerusalem. Instead, he kept going, driving the two-hour journey to the holy city for her.

He was his mother’s favourite, her first-born child, but he would later drift apart from his father. They had once hiked, travelled and walked their dog, Gingi the golden retriever, together. 

Khalid remembered being a content child. “I was happy; it was okay. I had a good life,” he said. Each child had their own bike, car and computer.

After finishing at Al Shamila High School, where he was described as a good student, he would travel to St Petersburg in 2010 for a year’s study, following in the footsteps of his father, who studied in the Ukrainian city of Kharkiv during the Soviet era. Khalid found St Petersburg cold and boring. In February of that year, his parents surprised him on his birthday, taking him around town in the hope of cheering him up. He would leave there to start university at Technion University in the Israeli coastal city of Haifa.

Everything would change when he returned to Israel. Khalid started to pray at a local mosque, finding a new group of friends who his family say were older than him – in their early thirties – suspicious and to whom they were never introduced to. Turning to religion in Umm Al Fahm, a city with more than a dozen mosques and a majority Muslim population, was not viewed as abnormal.

“He stopped everything basically,” his sister said. “He did his prayers and met with his friends that we’ve never met. We took it as part of growing up.”

Before renewing his faith, Khalid smoked shisha and did not observe Ramadan. His father’s bottles of whiskey used to go missing, taken by his son to drink with friends. “We found out afterwards that he was stealing them,” he said.

When asked if, upon his return, he was looking for something to fill the hole he seemed to have in his life, Khalid answered in the affirmative. He was “really confused about what he was going to do with his life,” according to his sister. His father says he wanted to become a veterinarian with a focus on horses, but was “always running from his reality”.

Khalid has no known previous convictions in Israel. Rather, his family believe his radical views were born among his new circle of friends and then reinforced online. It was in these arenas that he became “brainwashed,” they say.

Before enrolling as an engineering student at the Technion, he would discover the sermons of the world's most notorious extremists, many of them on YouTube. They included former Al Qaeda leader Osama bin Laden, Abu Musab Al Zarqawi, the leader of Al Qaeda in Iraq, the precursor of ISIS, and Abu Mohammad Al Adnani, ISIS’s former mouthpiece.

“I found what I want…what I believe in,” he said.

He would not graduate. 

Khalid stopped attending his classes at the Technion during his first year. “It turns out he is meeting with his friends in Haifa, maybe,” his father said. “He never told us what he was doing there or with whom.” Khalid dropped out of university after one year. His father told him to make something of his life; this was the beginning of the deterioration in their relationship.

“Go to work! Make your life! Marry!” Mousa recalled telling him. He was met with a muted reaction. Mousa also confronted Khalid about his new group of friends, who he denied existed. Eventually, he said he and his wife “bit our lips”, thinking their son's problems were part of his transition into adulthood.

The Technion confirmed his attendance to The National but would not divulge any further information so as not to contravene the “right to privacy” of their current or former students. 

After moving back home, Khalid picked up odd jobs at a supermarket and a local bakery. But, ultimately, these did nothing to lead him away from the life he was about to choose. 

After travelling to Adana with his two friends and being smuggled into northern Syria, the trio would join Liwa Al Tawhid, a rebel group that has co-ordinated attacks with Al Qaeda’s former affiliate Jabhat Al Nusra. Khalid, then 23, said he and his friends wanted to fight Shiites, specifically the regime of Bashar Al Assad, because of his crimes against Sunni Muslims since the civil war began.

“I was like: ‘hey people, the borders are open.’ In Turkey, there were no passports, no documents," Khalid said. "Going in and out, it was something easy. So I said: ‘hey, let’s go’”.

Once in the northern city of Aleppo, he received battlefield training before he and his unit defected from Liwa Al Tawhid to ISIS, considering them to be too moderate. He would then spend time in Sheikh Najar and Al Bab, cities north-east of Aleppo, before heading south to Homs.

For almost four years, he would serve as a frontline fighter for ISIS and – because he spoke Russian – as a translator and manager for the group’s Chechen and Dagestani contingents, who were notorious for their brutality. Khalid said he would help them buy goods from the market in Raqqa – the eastern city that once served as ISIS's so-called capital – and liaise with Arabic-speaking members of ISIS.

As ISIS lost territory, Khalid moved east. Starting in Hama, he would move to the ancient city of Palmyra, then Raqqa, before living his last days of freedom in the eastern province of Deir Ezzor. His family say he is believed to have married in his first year in Syria, and confirmed to them on the phone that he has two young children. Their whereabouts are unknown and Khalid did not mention them in the interview.

In the December 2017 raid to capture Khalid and his fellow fighters, the Americans arrived in Humvees, aided by drones and a manned aircraft, according to his recollection. He ran out of ammunition, so surrendered to the US forces. He says it was such a large operation he thought its target was the fugitive ISIS leader Abu Bakr Al Baghdadi. The world's most wanted terror chief killed himself during a US commando raid in northern Syria in October this year.

Asked if he had killed anyone in those three years as a member of ISIS, Khalid said that detail slipped his memory, perhaps conscious of the potential for a future trial. But he happily admitted that he fought for the group.

“Well I can’t say for sure, but I was in a battle where people were killed. But if it was me, I don’t remember that. I don’t know for sure,” he said.

About 60 Israeli Arabs left to join ISIS, a small fraction of the 1.6 million Arabs who live in the country. This is also a much lower figure than the number of foreign recruits from Europe and elsewhere in the Middle East and North Africa. 

Others tried unsuccessfully to join ISIS, including a man who paraglided into Syria from the Israeli-occupied Golan Heights before being tortured by both the militants and the Syrian regime. Experts say many Israeli Arabs or Palestinians who hold extreme views are more likely to tie themselves to the radical elements of the struggle against the Israeli occupation, instead of an international terrorist organisation. ISIS rejects nationalism, so the Palestinian focus on national liberation ultimately dilutes the extremists’ attractiveness for many Arabs in Israel.

Khalid’s relatives say they identify with both Israel and the Palestinians, with a leaning towards the latter. Khalid himself said the Israeli-Palestinian conflict is the “main cause for Muslims everywhere”. But why would a disaffected Israeli Arab of this opinion want to join ISIS and not a group like Hamas, which rules Gaza and has fought Israel three times in the name of that cause since 2008?

“That’s a whole different thing. These are democratic people. We’re not democratic, we’re not communist. This is Sharia that we’re ruling with,” he said. “The Muslim Brotherhood is a whole different thing from Islam.” Although far removed from ISIS, Hamas is widely accused of anti-democratic practices. It has not held an election since 2006 and has repressed protests and expressions of dissent in the coastal enclave.

According to counter-terrorism officials, two main factors account for this small number of Israeli Arabs joining ISIS: their identity and their treatment at the hands of the Israeli government.

“Most of the Islamic State supporters among the Israeli Arab population identify themselves as Arab or Palestinian. In no way do they consider being Israeli as part of their identity,” Aviv Oreg, former head of the Israeli military’s global extremism desk, said.

But Khalid said he did not leave because of Israel as a state, nor because of its government, although he refers to growing up as a second-class citizen in a country where the Arab community has long complained of widespread discrimination.

“Marginalised? Yes. But I didn’t care about that,” he said.

The Shin Bet approached and questioned him at least two times before he left for Syria, he said.

“Like two, three times. The last time, I remember, he said ‘hey, you’re going to Syria. I know you.’ I said I don’t want to go to Syria,” he claims, in reference to a Shin Bet agent.

Khalid faced many questions about his Israeli passport, both in Turkey and in Syria, but was never accused of being a spy within ISIS’s ranks, he said. But ISIS confiscated his passport when he joined the group in Syria, according to the Kurdish intelligence agent.

Khalid proceeded to express glee about the death of one of his fellow Palestinians, who was accused of that very crime, because he feared he had joined the group to spy on fighters like him, based on no evidence but the group’s word. In 2015, an ISIS propaganda release showed a child, ordered by a French militant, shooting and killing the alleged spy, 19-year-old Mohamed Said Ismail Musallam from occupied East Jerusalem.

It was Khalid’s belief in every word uttered in the video that illustrated how gripped and warped by the group’s propaganda he had become, and remained. 

Musallam read what was likely to have been a prepared and coerced confession, saying that he worked with Israeli intelligence and had travelled to Syria to spy on ISIS from within. 

The slain man’s family said he had no ties to Israel's Mossad spy agency, but was instead lured by the promise of women, money, villas and paradise.

“I remember the video. It was fun,” Khalid said. “That was the happiest thing I ever saw in the Islamic State.”

The bags under Khalid’s eyes give him an intense, delirious gaze and he speaks softly but incoherently in a chronic slur. These could be tell-tale signs, according to psychologists, of someone who has been confined without any human interaction for long periods.

Upon arrival, many inmates choose not to speak for days, one prison staffer said. But, despite living in solitary confinement for almost 24 hours a day, Khalid joked with his guards, who say that they have formed friendships with prisoners in order to retrieve information and create a calmer atmosphere at the facility.

None of this masks Khalid’s views, which he talked about openly. He is a man who defends slavery, rape and the beheadings of Western hostages that propelled ISIS to notoriety in 2014. He said he had no knowledge of James Foley, the US journalist whose killing the group famously broadcast to the world, but said he supports his murder because of his profession.

“If they are captured, they are killed; that’s it. There’s no such thing as a journalist. If he was a journalist or a soldier, for us that is the same thing,” he said.

On slavery, he said that “people taken as slaves, this is something religious, something in the Quran. [If] they refuse to embrace Islam, and they refuse...they refuse to be under the Islamic State’s judgment and live under the Islamic State’s sharia, these people...their men will be killed and their women will be taken as slaves.”

After the death of Al Baghdadi and the end of ISIS’s territorial control in Iraq and Syria, Khalid’s case offers a rare glimpse into the mentality of the foreign ISIS fighters who want to continue the group’s battle for supremacy. 

An array of foreign fighters have pleaded to come home from Middle Eastern prisons. In a July interview with BBC Arabic, another captured Israeli Arab fighter, Sayyaf Sharif Daoud, begged Israeli Prime Minister Benjamin Netanyahu to bring him home. But Khalid does not seek repatriation.

“It’s great. I’m happy about that,” he said of Israel’s decision to reject his return.

“They lied to me [in Baghdad]. They said the Israeli intelligence is interested in you; you’re going back to Israel. That was the worst day of my life,” he said. “I got down from the chopper and found myself here in Kurdistan. I was happy.”

When given the news that ISIS leader Al Baghdadi had killed himself in a US special-forces raid, Khalid was unfazed. He has retained the group’s apocalyptic vision and belief that dominance is on the horizon. He said the group will re-emerge even stronger after the crushing defeats in Iraq and Syria.

“If [Baghdadi] was killed, this is something normal. So many leadership killed, but jihad continues,” he said. “I can assure you, in just a few months - not years - it’s going to regain its power. It’s going to grow big. We all know what’s coming next. It’s a big war.”

Kurdish officials estimate that thousands of ISIS fighters remain in mountainous areas of Iraq, using the inhospitable terrain to rebuild the group’s strength. Khalid says the group will eventually capitalise on growing friction between the US, Iran, Russia and Turkey in the Middle East to create an even larger proto-state than before, when it controlled territory roughly the size of Britain.

“It’s gonna become something big, a lot bigger. This time it’s Damascus and Baghdad, not just Raqqa and Halab,” he continues, using another name for the northern Syrian city of Aleppo.

He said the US will “sink with [US President] Donald Trump” as he is “running for oil, fighting everybody for oil”. This suggested that Khalid had learned the news about the US withdrawal from northern Syria, which allowed Turkey to launch a deadly incursion. After much persuasion and backlash, Mr Trump would eventually leave a residual force of 500 troops to guard and sequester Syria’s oil from its fields in the country's east. But Khalid said he had “no news for 21 months,” the length of time he has spent in solitary confinement.

It is likely that thousands of ISIS foreign fighters still in captivity or at large in Iraq and Syria share Khalid’s views. Mr Trump has said the group had been defeated but terrorism experts have poured scorn on that claim, saying that ISIS’s ideology lives on in young men and women like Khalid. 

Did he have any regrets? “No. Never, never,” he said. Would he join the group if he was released tomorrow and do it all over again? “Definitely,” he said, without hesitation.

Khalid’s radical and unswerving outlook on the world is most probably the very reason why Israel not only does not want him back, but refuses to declare him as ever having been one of its own.

The special forces commando, tactical knife strapped to his back and assault rifle hanging from his shoulder, said the uncuffed militant was well trained and would be able to kill those before him “in a minute”.

Khalid's jailers considered him to be so hardline, his beliefs so extreme, that the prison staffer admitted they did not want him to mix with other detainees. Even though the unapologetic fighter is happy to admit to being part of ISIS, he is yet to stand before a judge. He said only his fingerprints had been taken, so far.

One consequence of the crimes committed by ISIS members and the wreckage the group left across Iraq and Syria is that there is scant sympathy for the conditions that captured fighters like Khalid find themselves in. Danish Foreign Minister Jeppe Kofod announced last month that his country had plans to stop consular assistance for all Danish foreign fighters. “We owe absolutely nothing to foreign fighters who went to Syria and Iraq to fight for ISIS,” he said.

Turkey, whose government says it is holding 2,280 ISIS fighters, has ordered the repatriation of dozens of European ISIS suspects, presenting those nations with a situation they had long tried to dodge. In a separate case, Ankara sent 39-year-old US citizen Muhammad Darwish Bassam to Greece, who refused him entry, leaving him in a strip of no-man's land. Bassam was pictured waving his hands in the air, stuck between two countries, a symbol of the global aversion to taking these suspects back. He will now be repatriated to his home country.

Khalid, with one of his guards in earshot, said the Kurdish authorities were treating him well. He receives three meals a day and toilet breaks. But he mumbled and laughed nervously when talking about his imprisonment and when describing his cell, which he said was less than 8 feet by 4 feet. The National did not see his living quarters.

When asked after the interview if it was acceptable to hold someone in solitary confinement for that long, a member of the prison’s security detail was frank about Khalid’s conditions: “What do you want us to do? Put him in a five-star hotel? If he gets out, he will kill all of us.”

It is a harsh tactic once used by the group itself. ISIS kept men in solitary confinement in the depths of a Raqqa football stadium, and it is believed that Al Baghdadi once held US hostage Kayla Mueller in similar conditions. 

Nonetheless, the impact of long-term solitary confinement on terrorist suspects has been widely documented and advocacy groups have expressed concern about the practice, saying it breaches international legal obligations, worsens security problems over time and harms their mental health.

"The prolonged solitary confinement of detainees held without trial likely violates human rights law prohibitions on torture and cruel, inhuman and degrading punishment and requirements that correction authorities respect the inherent dignity of each inmate," Sarah Leah Whitson, Human Rights Watch's executive director for the Middle East and North Africa, said.

Three Israeli human rights organisations declined to comment on Khalid’s case. One prominent Israeli NGO worker ascribed their hesitancy to speak for this story to a fear of being linked to the case of an ISIS fighter at a time when the right-wing government of Prime Minister Benjamin Netanyahu is increasingly marginalising the sector.

Agnes Callamard, the UN special rapporteur on extrajudicial killings, said that although she could not comment on the specifics of Khalid’s case because she does not have proof of his Israeli citizenship (ISIS took his passport from him in 2013), a state's refusal to bring home a citizen living in solitary confinement without trial was likely to constitute a serious breach of international law.

"If there is evidence the person is a citizen; that he is held under conditions of detention amounting to inhuman or degrading treatment or torture; if his life is at risk, then his country of citizenship has the obligation to take all necessary actions to protect him," she said.

"Under the current conditions in Iraq and north-eastern Syria, protection requires repatriation. Protection does not mean immunity or impunity. Upon return to their countries of nationality, these individuals must be investigated and prosecuted for their crimes."

Khalid’s family argue their case for bringing him home from legal and moral standpoints.

“If he was dead, it would be better for him than being in this situation,” Tala, his sister, said.

Membership of ISIS and fighting for the group are acts of terrorism in both Iraq and its Kurdish region. Khalid’s family agreed that he should face justice, but want it to be handed down where he was born and raised. 

“Even if it’s 10, 15 years here in prison, it would be better. At least we [would] know where he is,” Mousa said.

The family have rarely talked about Khalid, either between themselves or in the media, for fear of reviving old memories. But they are now speaking out after The National’s disclosure in the hope that Israel’s government can repatriate him to face his punishment at home.

“We’re now discussing the options, if there is any way to bring him back home,” Tala said. “For now, we have no idea what is going on.”

The Israeli government is unlikely to make such a U-turn. It regards militants like Khalid as traitors, undeserving of repatriation or even citizenship. Although Israel only first moved to strip an Israeli Arab extremist of their citizenship in 2017, a case still pending, it is a 2008 law that authorises the country's courts to take citizenship from Israelis convicted of terror-related offences and judged to have abandoned their "loyalty" to the state. It is a tactic that Israeli lawyers have argued has been used to discriminate against Arabs even if it is not followed through.

In April, Interior Minister Aryeh Deri announced that this process had begun for one particular ISIS fighter, Abdullah Hajla.

“We are talking about a dangerous man to the State of Israel,” Mr Deri said. “I do not see any course of action other than revoking his citizenship. He is not worthy of being an Israeli.” That process has stopped, as Israel believes him dead, the Interior Ministry said.

The ministry official confirmed that Hajla never possessed a second legal name at any point while living in Israel, ruling out the possibility that the authorities believed him to be the same person as Khalid, even though they left for Syria in the same year.

In Hajla’s case, he holds a second citizenship of an undeclared country. Khalid does not have that, according to his family, meaning Israel is unlikely to have stripped him of his sole citizenship.

Israel has only successfully removed its citizens’ nationality on a few occasions, according to Yoram Schweitzer, former counter-terrorism adviser to Mr Netanyahu and head of the terrorism programme at the Institute for National Security Studies. 

“Israel has rarely revoked citizenship for terror offences,” he said. “Only twice and only against those who were involved in lethal operations and had dual citizenships so they could find an alternative state to absorb them.”

Governments have been less hesitant to strip their citizenship from fighters with dual nationality, as opposed to making them stateless, which would contravene international law. For instance, British ISIS members Jack Letts and Shamima Begum are both in Syrian Kurdish prisons and Britain has moved to revoke their UK citizenship.

Letts has Canadian citizenship, and Britain claims Begum is eligible for Bangladeshi citizenship, making it a more palatable decision for the British government, although Dhaka has rejected that assertion and Begum is now appealing against the bid to remove her British nationality. Legal experts have criticised such decisions on dual nationals as only pushing the problem on to other countries.

With the Israeli authorities remaining silent on Khalid’s case, the question of his citizenship status still remains unanswered.

Yet Khalid’s father, unfazed, issues a plea for his son’s return anyway.

“They must take him back; they should take him back, and punish him as an Israeli citizen,” he said.

It appears, however, that Israel does not deem Khalid, as Mr Deri articulated, worthy of being an Israeli. It may also be that Israel’s security services have considered him a danger to his compatriots, which from his still-held views is likely. Israel has only suffered one ISIS-claimed terror attack, a 2017 shooting in Jerusalem, the claim of which Israeli and Hamas officials disputed, but it remains a national security concern.

The Israelis may have bargained with the Iraqi Kurds to keep him under their watch, and therefore cannot speak about his case. It may be a confidential file ordered from the top, so no authority can discuss his case. There are many possibilities.

Mr Oreg has no specific knowledge about Khalid’s case but says Israel is likely to be refusing to admit to his past life in the country because it is part of the "global approach" to those who left home to fight for ISIS.

"We are talking of people that have decided to [turn] traitor [against] their countries and join the ranks of their declared enemy," he said. "They must be accounted for and pay the sanction involved. ‘Sorry’ is not enough. The message to the entire society is that one must be accountable for his decisions in order to [dissuade] others from making a similar move."

But Israel refuses to concede that Khalid even lived on its soil for more than two decades, or that he still has a family in the country.

It is an unusual abandonment of a legal citizen, one that at least five prominent European and North American terrorism experts contacted by The National – Jason Burke, Amarnath Amarasingam, Colin P Clarke, Pieter Van Ostaeyen and Guy Van Vlierden – say they cannot recall seeing before, be it for an ISIS or Al Qaeda foreign fighter.

There may be other cases like Khalid’s not yet in the public domain, but there is no evidence that a government has completely refused to acknowledge a fighter’s belonging to the state in the full knowledge that he or she is one of theirs.

In any case, the family believe that the Israeli authorities know about Khalid and his presence in northern Iraq. They say they were questioned about him on numerous occasions at Ben Gurion Airport before Khalid’s capture in December 2017.

“Whenever we went out, whenever we came back, we would be stopped for investigation,” Tala said. “They asked me where he was, if I knew anything about him. And we were not speaking to him; we hadn’t heard from him in like a year and a half.”

But this questioning stopped after his capture, leading them to believe the Iraqi account that he was refused entry.

“That’s why the investigation stopped. Now they know. Now we go out of the airport and we go back in and there’s nothing happening. It’s all back to normal,” she said. “I do believe that Israel has knowledge of his existence and his presence in Iraq. Israel does not just let go of things easily.”

The Kurdish intelligence agent said there was no co-operation with Israel on Khalid’s case because there are “no connections between Iraq and Israel” in public. Iraq does not recognise Israel as a state and they have no formal diplomatic relations.

Israel has, however, maintained a covert relationship with the Iraqi Kurds on several levels, including intelligence. Israel has supported the Kurdish struggle for independence from the federal government of Iraq, an as-yet-unsuccessful campaign that keeps their relationship in the dark. In return, the Iraqi Kurds helped to repatriate Iraq’s last Jews to Israel.

The family cannot travel to northern Iraq to see Khalid, and it would be unlikely that they would receive permission to visit him, even if they could. But what would they say to him in that event? Mousa said he would “yell at him and fight him”. Tala said she would spend time with him like they used to.

“I don’t really have anything to say to him. I would probably take some ice cream and eat it with him,” his sister said. “Vanilla was our thing.”

Having new information about Khalid has provided the family with something to hold on to, she said. “We were basically waiting for any news … even if he’s dead, then okay that would be closure also. It would be a sad one but it would be closure,” she said.

For Khalid, there is likely to be little closure. His future is bleak. No state wants him, and he is yet to face trial, if at all. 

But he says he is certain of several things: that he never wants to return home, that the death cult he devoted himself to will rise again, and that he has no fear about whatever awaits him next. 

That may include the death penalty, which remains an option if he is returned to Baghdad’s custody, where at least a dozen foreign fighters have received such sentences after short trials, and where rights groups say other detainees have been tortured. The death penalty remains an available punishment in Iraqi Kurdistan, but it is rarely used, according to Mr Talabany.

“I’m not afraid of anything,” Khalid said. “When that time comes, [when] I’m gonna be released, the caliphate will be something big. Everybody will be raising hands. That’s it.”

It remains unclear what will happen to Khalid from here. The Iraqi Kurds would not be drawn on what they will do with him next, probably unaware themselves about what lies ahead for him. There is little chance of him ever setting foot inside Israel again. His government – barring a drastic change in power – may never acknowledge that he was one of their own. Mousa and Hanan will never get back the young boy they loved, the first-born son who once dreamed of saving horses, nor will Tala, the brother who was once her best friend. 

Khalid’s case says a lot about the security complex of Israel, a country surrounded by Middle Eastern nations – Egypt, Syria, Lebanon and Jordan – who have suffered ISIS insurgencies or ISIS-claimed attacks. It is now front and centre of the campaign to deny ISIS foreign fighters any due process.

The revelation, by chance, that Khalid is alive after three years has at least provided his family with a semblance of comfort amid the pain of losing their son to ISIS in the first place.

The family still hangs pictures of Khalid standing alongside them on their walls, images of better times. Mousa remembers that, when his boy was two, he would smell and kiss the flowers in the garden instead of picking them.

He pauses before letting out a wail that carries six years of emotion. He breaks down at the thought of Mohammed as an innocent child, knowing that his son is still alive, albeit not the boy that he once knew.

Willy Lowry contributed reporting.