Last December, Amir received a message from a local number he did not recognise. It said: “Your son has become a martyr."
It was news he had been dreading for months, since his son unexpectedly vanished from the family home in Russia’s north Caucasus republic of Dagestan.
“I don’t even know where he got a passport,” said Amir, who did not give his real name for security reasons. “He called from Turkey to say he would be studying for a while and would not be in touch. That’s the last time we spoke to him.”
In fact, the young man had quickly crossed the border to Syria to join the Islamic State of Iraq and the Levant (Isil), following in the footsteps of hundreds, if not thousands, of others from this corner of Russia.
Russia's position as one of the most important suppliers of foreign fighters to the terrorist group was thrown into the spotlight last month when three former Soviet citizens, including two Russians, blew themselves up in a coordinated suicide attack at Istanbul’s Ataturk airport, killing 45 people.
The attackers did not include Amir’s son. But at least one bomber, 24-year-old Vadim Osmanov, was from the same region of southern Dagestan.
No one knows exactly how many Russian and former Soviet citizens have joined Isil. The anti-terrorist centre of the Commonwealth of Independent States, a loose grouping of former Soviet countries, has put the figure at 5,000.
Russian president Vladimir Putin said in October 2015 that 7,000 citizens from all former Soviet States, including Russia, had gone to join the terrorist group. In reality, independent experts say it is almost impossible to come by accurate figures.
Keeping score is complicated by the fact that many Russian speakers have joined rival outfits such as al-Nusra, the group formerly aligned with al-Qaeda. Nusra renamed itself Jabhat Fateh al-Sham (Front of the Conquest of Syria), in July.
Isil's command structure is notoriously opaque, but experts believe the group fields at least three exclusively Russian-speaking “Caucasian” battalions of about 150 men each.
Often led by Chechens, the rank and file of these battalions is believed to have been drawn from across the north Caucasus and other parts of the former Soviet Union.
A number are believed to have taken up residence in Isil's Iraqi stronghold of Mosul, where they are said to enjoy a degree of privileged autonomy.
“They have a reputation for being pretty fearless fighters, which is why they move quite quickly up the hierarchy,” said Ekaterina Sokiryanskaya, an expert on the North Caucasus with the International Crisis group.
The fighters include some of the most notorious figures in Isil’s reign of terror, such as Omar Shishani (born Tarkhan Batirashvili), an ethnic Chechen from Georgia who was considered so influential that he was described as Isil's “minister of defence.”
Isil confirmed that Shishani, 30, was killed in battle earlier this month.
Anatoly Zemlyanka, a Siberian-born “Jihadi John”, gained infamy when he beheaded a fellow Russian citizen in an execution video published last December.
The attack on Istanbul airport is believed to have been coordinated by Akhmed “one handed” Chatayev, a 36-year-old from Chechnya who, like Shishani, is considered an influential commander among Isil’s Russian-speaking battalions.
Rising from the Caspian coastal plane to the towering Caucasus mountains on the border with Azerbaijan, Dagestan is a part of Russia that feels more Middle Eastern than European.
The major cities of Makhachakala and Derbent are dotted with mosques rather than churches; many - though by no means all - women wear the hijab, and alcohol is available but noticeably discreet.
Throughout the 2000s, jihadists loyal to a movement called the Caucasus Emirate launched attacks across Russia’s north Caucasus republics, often in Dagestan. As recently as 2011, they were carrying out suicide bombings against civilian targets in Moscow.
But as the civil war intensified in Syria, Isil recruiters began deliberately targeted the region, luring potential recruits away from the demoralised Caucasus Emirate to fight “five star jihad” in the Middle East.
Russia’s intelligence services, anxious to prevent attacks on the 2014 Winter Olympics in Sochi, are believed to have turned a blind eye and in some cases actively facilitated the travel of known insurgents to fight in Syria.
Combined with a ruthless crackdown ahead of the Olympics that killed dozens of fighters, including Caucasus Emirate chief Doku Umarov, the capacity of Dagestan’s jihadists to operate at home has been massively eroded.
“There’s not more than 100 fighters still in the woods in Dagestan,” said Sevil Novruzova, a Derbent-based activist who helps fighters seeking to surrender negotiate amnesty with the authorities.
In contrast, she said she was aware of around 650 individuals from southern Dagestan who left for Syria.
The outflow is not restricted to men. Activists say increasing numbers of women are travelling to Syria, sometimes accompanying their husbands but often to seek jihadist husbands. In at least two cases the Telegraph is aware of, married women abandoned their insufficiently devout husbands in Dagestan and took their children with them to Syria.
As Isil loses ground in the Middle East, the potential return of local fighters is worrying the Russian government. Russian security forces carry out “special operations” in Dagestan’s rural areas almost weekly and Alexander Bortnikov, the head of Russia’s Federal Security Service, has said that his agency is monitoring 220 individuals identified as potential suicide bombers.
"We have documentary confirmation that leaders of groups sheltering in a number of Middle Eastern countries are planning to continue their terrorist activities and to try to give new impetus to the North Caucasus insurgency," he told a conference of security chiefs last week.
Experts, lawyers, and community leaders in Dagestan point to a myriad of reasons for the continuing radicalisation of local youth, including unemployment, failing public services, and the brutal counter-insurgency methods employed by the Russian security services and police.
Officials blame much of the radicalisation on the growing influence of preachers of Salafi Islam, a conservative branch of the faith that has emerged as a competitor to the Sufi Islam traditionally followed in the region.
Abdurakhim Hadji, a Salafi imam in Novosasitli, a conservative village in Dagestan’s Khasavyurt district, said he was horrified by violence and would advise anyone who asked him not to even think about going to fight, either in Syria or “in the forest” in Russia.
At least 20 men from the village have left to fight in Syria, and the village has in the past been harassed by both Islamist fighters and security forces fighting them.
Mr Hadji said the spectre of terrorism had been used as an excuse for a counter-productive crackdown on conservative believers.
“Those who are not Sufi, they call Wahhabists,” he said. “And since very few Sufis have gone to fight, it allows them to say that all Wahhabists are terrorists,” he said, after leading evening prayers in the village. Instead, he points to deeper historical roots of the recent decades of unrest. “Dagestan did not voluntarily become part of Russia. Russia is an empire, and Dagestan is a colony,” he said.