The family of Ali Amin Abdullah make unlikely Islamic State supporters – not least because they are from the Shia sect, despised and persecuted by the jihadi militants. In order to survive for two years under the self-proclaimed caliphate in Mosul, however, they did what it took to avoid persecution and likely death at the hands of Isis fighters: they pretended to be Sunni. For Abdullah, who was repeatedly threatened by gun-wielding militants who were suspicious about his true denomination, this meant more than just words: he signed on for classes at a local Isis-linked religious institute. But his subterfuge proved so successful that, when newly arrived Iraqi government troops came to the family’s home in early November, they accused him and his relatives of collaboration. “When I opened the door, a soldier said: ‘He is Daesh,’ and detained me and then took my brother, Abbas, too and asked about my father,” said Mustafa Ali, one of Abdullah’s sons, using a common Arabic acronym for the group. His father shouted: “I am not Daesh,” but the three men were taken to a nearby base. Though his sons were eventually freed, Abdullah was taken away. His family, who insist there is no evidence he ever supported Isis, much less took up arms, have had no news since of what charges he might face. Their anger is growing by the day, the initial joy of freedom inspired by the anticipated removal of Isis from Mosul transmuted into fear. “If my father was Daesh,” said Ali, “he would be fighting the army in the battlefield, not sitting in his house waiting to be detained by the army.” It is a year since the Iraqi city was liberated, but people are slow to return, reeling from the damage inflicted by their former captors The family’s struggle underlines the huge challenges ahead for the Iraqi authorities, even if they manage to win the difficult military battle to fully wrest control of Mosul from the group. When the fighting is done they must reassert control over a city of more than 1 million people, while weeding out Isis members and supporters trying to go underground as the core of a future insurgency. Allowing militants to slip through the net to form sleeper cells or work as covert recruiters could put the city at risk in years to come. But too harsh a crackdown, among citizens who have been wary of the central government for years, carries serious risks of its own. As it tries to rebuild the city, Baghdad needs support, not resentment, from Mosul’s residents. But the story of Ali’s family suggests the Shia-dominated government is alienating even people who should be natural allies. Hailing from the tight-knit Shabak minority, which has lived for generations in the Nineveh plains, a traditional haven of diversity, the family thought they had become inured to bloodshed after surviving the descent into vicious sectarianism that followed the US-led invasion in 2003. So despite grim reports of life under Isis rule, most decided to risk staying on rather than flee to an overcrowded, underfunded refugee camp, relying on passing as Sunni Shabaks. But then Isis arrived, and Ali realised nothing had prepared him for its twisted dedication to murder and cruelty, the markets full of Yazidi women sold to be raped, or the vicious, bizarre executions on trumped-up or trivial charges. Mosul residents cower in their homes beneath the bombardment – but fear sectarian violence from Shia militias once the besieged city is liberated from Isis “We have seen too many beheadings, people being drowned in cages, thrown from the top of buildings,” he said. “I myself saw a man thrown off a building near the governor’s office around three months ago. I couldn’t sleep for a week afterwards.” In the first days after the militants swept into town in 2014, his family feared they had made a terrible mistake, after Abdullah was arrested twice and threatened at gunpoint by militants convinced that the family were Shias. “They placed a gun on my father’s head four times but he insisted that he was a Sunni,” Ali said. Increasingly fearful for his family after his second brush with Isis, Abdullah decided to sign up for a sharia law course in a school linked to the group. He hoped the relatively innocuous cover of extreme devotion would provide some protection if attacks escalated. And when Isis came to arrest him for the third time at the end of 2014, it was the head of the sharia school, Sheikh Hammadi, who secured his release by vouching for his Sunni credentials. Even Hammadi’s word could not put suspicions to rest, and Isis rounded him up again in 2015. By then his protector had been killed in a US airstrike, but his fellow students came to the rescue instead. He could not be Shia if he was studying Sunni texts in an Isis school, they argued. Displaced Iraqi people, who fled the Islamic State stronghold of Mosul, gather at Khazer camp in Iraq. Photograph: Ammar Awad/Reuters The head of the local neighbourhood committee, who stayed through Isis rule, confirmed key details of the family’s story to the Guardian. “I can tell you with certainty that the family of Ali Amin [Abdullah] is Shia,” said Mohammad Sulayman Yunis, 65. “Isis forced him to study sharia because they suspected him of being Shia, and he would have been killed if they proved he was Shia. They destroyed many Shia houses in Gogjali [a neighbourhood in Mosul]. I was there and saw it myself.” Ali, a tall, inquisitive man, was well aware of the threat. When the Guardian first contacted him through two intermediaries to ask about life in Mosul, Ali agreed to speak about the Isis horrors he was witnessing as the Iraqi battle to reclaim the city began – even though possession of a sim card could mean a death penalty. Most nights in October he would walk up to the roof of his cement block house, look around for informers who might be tempted to turn him in, then slide under a blanket and take out his phone. “All we need to do is to get rid of this threat. We will not need anything after that. Mosul has become a prison,” Ali whispered into the handset one night. Sometimes he was with his brother-in-law, who had been whipped by Isis for keeping his beard too short and for smoking. The city became even more dangerous as the fighting closed in and Isis seized civilians to serve as human shields. Food ran low but people stayed home and went hungry, hoping to be spared. “No one knows where the next mortar will hit,” said Ali, who used to drive a truck before Isis came and cut off most trade along with his livelihood. Then in late October, a couple of weeks after the launch of the offensive to oust Isis, there was a glimmer of hope, as the militants began retreating. “I was in Mosul market yesterday for an hour; people are busy collecting food stores. I did not see any Hasba [morality police] in the market. We were around 15 people who did not go to pray and no one told us to go,” he told the Guardian at the time. When government soldiers arrived in their corner of the eastern suburbs of Mosul on 2 November, Ali thought freedom was in sight. The nightmare of life under Isis, he thought, could be drawing to a close. But it was then that the cover that had kept their family alive – the pretence of being Sunni – turned into a liability and soldiers took Ali, Abbas and Abdullah away. The family finally fled Mosul on 13 November, deciding in the unbearable calculus of war that the risks of the road were less than the risks of staying under attack. They could do more for their father alive than dead, they decided, and were told he had been moved to the capital. “They have taken my father to Baghdad and we don’t know what has happened to him. He is innocent,” Ali said, before leaving for the capital to look for him. There is no more news on where Abdullah is being held, but Ali has vowed to keep searching as long as he can afford to. His Facebook page is filled with the search. One picture shows Ali’s toddler son holding a mobile phone to his ear, above the caption: “He is waiting for you to return.” Another simply shows a young man screaming into the sky. “Oh Allah, I am tired, please return my father.” In Guardian stories previously quoting Ali, he was given the pseudonym Abu Mohammed and his name was altered. This was to protect him given Isis penalties for owning a mobile phone and criticising the group’s rule.