Long before Khatoon Khider took up a gun, she became famous for singing about another woman who went to war, a tragic heroine who followed her lover into battle in disguise. And she wondered even then, years before the Islamic State had been created and nearly a decade before its fighters’ murderous rampage across her homeland, if she might one day have to go to war herself.

After what has happened to the Yazidi women, I decided to stop singing until I take revenge for them

Khider, whose chin and cheeks are marked with the tiny dark-blue tattoos distinctive to the region, was born into Iraq’s Yazidi minority. Their small numbers and ancient, unusual religion with a peacock angel and taboo around the colour blue, have brought centuries of persecution, so the musical tradition she inherited is heavy with stories of war, massacres and loss. Her own life, too, has been marked out by conflict, near and distant.

“We have spent all our lives in wars, for no reason,” she says, sitting in the barracks to the north of Mount Sinjar where she now lives, after a dawn drill with her fighters. Her father was conscripted to fight in the Iran-Iraq war months after she was born, and taken prisoner soon after. She would not see him for a decade, and believes his absence shaped the singer she became.

“When I was a kid, my grandfather and mother were always crying and wailing over my dad in Iranian captivity, and something pushed me to express that sadness,” she remembers. “I never lived through a good time. That is what made me a singer.” Khider’s family were shepherds and musicians. She was born on the high summer pastureland of Mount Sinjar where they camped for months each year, fattening the herds, and grew up surrounded by songs, intoxicated by her musical heritage.

Facebook Twitter Pinterest ‘We don’t really care about our houses and belongings. They aren’t worth the life of a single young child’: Khider, with other women from her troop, reflects on their motivation. Photograph: Alessandro Rota/The Observer

She had to leave school after the sixth grade to work as a day labourer on local farms. Sanctions on Saddam Hussein’s government had pushed up food prices, the family needed more cash, and there was no high school in her town anyway. With the songs of her childhood playing in her head as she worked, she asked her brother-in-law to find her a tanbour, a guitar-like stringed instrument and taught herself to play. Her relatives soon gathered round to listen to her own takes on their favourite ballads but, as a woman in a conservative society, she never expected anyone beyond her relatives to hear them.

“I sang at home, but my father never noticed,” she says. “I didn’t want to perform in public, because of our culture, which does not have space for female musicians traditionally.” It was a cousin who launched Khider’s career, when he saw a commercial opportunity for himself in her talents. She did not even understand how a camera worked when he invited her to sing for the family and made a secret video recording of the session.

The shaky CD sold nearly 4,000 copies, an extraordinary number for a poor, low-tech society. The sudden fame embarrassed Khider, who feared it brought only shame, until her father offered his support. Sheikh Ali Shamsi was virtually a stranger to his daughter when he was released from captivity at the end of the 1980s. “I went to meet him at a checkpoint when he was released, and there were two guys with him, fellow prisoners who had become friends. They had seen pictures of me, and recognised me before I recognised my father,” she says.

But she discovered that when it came to women’s rights, he was a radical who would prove her biggest champion in music and war. “You should have told me you want to sing, and I am OK with that,” he told her when she was invited to the largest regional town to sing at a Yazidi celebration with all the community’s leaders in 2004.

Facebook Twitter Pinterest On the move: Khider drills her troops at their base in Snuny in Sinjar province. Photograph: Alessandro Rota/The Observer

It was her first performance in front of a crowd and she was almost paralysed with fear until she noticed one of the dignitaries on stage was weeping silently. He told her later he was moved not only by the song, but also the singer, the first Yazidi woman to perform their music in public. “Actually when I decided to be a singer, it was like going to the frontline and fighting the enemy, it was very difficult to choose this profession as a woman,” Khider remembers with a smile. Perhaps it was no coincidence that the song which sealed her fame, and foreshadowed her future, was the story of a woman who went to war.

The heroine Adule disguised herself as a man, enlisted as a soldier and formed a unit of under-cover women fighters, just so she could follow her lover to the frontline. She did eventually find him, but it had taken so long that he was sick with grief at their long separation. The shock of a reunion overwhelmed him, and he died in her arms.

“That’s how life is, you go through bad moments, happiness, sadness,” she says. The songs were usually tragic, but for her those years were filled with the joy of music and fame. “The singer’s life is the best life,” she says, allowing herself a moment’s lament for a life swept away, along with homes and villages, by the arrival of Isis fighters in the Yazidi heartland of Sinjar.

In the summer of 2014, they rampaged through her homeland and her own family home, murdering, torturing and enslaving her people, her friends and her family. Within months she was in uniform, driven by a furious desire for revenge.

Facebook Twitter Pinterest All that remains: the unit on patrol in Sinjar city. Photograph: Alessandro Rota/The Observer

Khider makes an unlikely soldier in many ways, quick to smile, a little dreamy and perhaps less lean than most commanding officers. “I haven’t had breakfast, I want to lose some weight,” she tells me with a smile, soon after supervising a dawn drill.

Isis believe that they won’t go to heaven if they are killed by women. They are not that brave

But she is entirely committed. She has sworn not to perform again until all her people are free, even if that means she never sings another note. “After what happened to Yazidi women and girls, I decided to stop singing until I take revenge for them,” she says. “Maybe I will go back to music, but I think this job as a soldier will be a long one.”

Everything of her past life has vanished anyway, the instruments and the mementos, even her home, targeted because her profession made her anathema to the militants. “When Isis came, the Arab neighbours who stayed [and collaborated] guided them to my house, because they knew I was a singer. They burned my photos and destroyed both my tanbours.”

An aunt was taken captive, a disabled uncle murdered in his bed and another uncle died on the frontline. She knew hundreds of others who were killed or enslaved, and the thought of the dead and the captive drives her on. “We don’t really care about our houses and belongings,” she says. “They aren’t worth the life of a single young child.”

She saw the horror first hand, because she was in Sinjar when Isis arrived and like hundreds of thousands of other Yazidis had to literally run for her life, into the mountains. Many were killed and captured as they tried to flee and, even for those who made it, the high slopes offered harsh refuge in the blazing heat of summer.

Facebook Twitter Pinterest Driven out: displaced people from the minority Yazidi sect, fleeing the violence in Sinjar. Photograph: Youssef Boudlal/Reuters

“I saw children dying of thirst and hunger, old people abandoned. I saw with my own eyes women throwing away their babies as they were running from the enemy because they were so afraid of being caught,” she remembers.

When the Yazidis were finally evacuated from the mountain, Khider was determined to return and fight. Her father, who first backed her to sing in public, also backed her unusual decision to take up arms and so she started lobbying the Kurdish Peshmerga fighters for weapons and the top Yazidi religious leader for his blessing.

“I told Baba Sheikh I want to fight Isis and he warned me: ‘It’s very dangerous for you as a woman, you may get caught,’” she remembers. “I replied that Isis had already taken our women from Kocho and Sinjar and other places, I am no better than them.” And so he gave her his approval. Formal permission from the Kurdistan regional government to set up a unit of women soldiers followed soon after, on 15 January 2015. After months of talking about her plans to fight Isis, this modern-day Adule already had dozens of women eager to join her “Daughters of the Sun”.

There are now nearly 200 women in the unit, some of them survivors of Isis’s slave markets, others driven to sign up by the fate of sisters or friends, cousins and aunts. Inspired by the Syrian Kurdish women who have led many battles against Isis across the border, and helped liberate Yazidis trapped on the mountain, they say the very existence of the unit is a blow to their enemy.

Facebook Twitter Pinterest Direct hit: smoke rises from the site of US-led air strike on Sinjar in November 2015. Photograph: Reuters

“Every day I am taking revenge. It’s a very shameful thing for Isis that women are fighting against them, they believe they won’t go to heaven if they are killed by women,” Khider says. “They are not that brave. They brainwash people and send them to war.”

It is a radical move for women in a traditional, conservative society, but the tragedy and horror of the Isis attacks have been so profound that not a single would-be recruit has been stopped by her family says Khider, who speaks to each woman and her family about the challenges and rigours of military life before they sign up.

Several are married to Peshmerga soldiers themselves. They wake at 6am and exercise, drill with weapons and then clean them. They take guard shifts with the men, and mostly wait for orders to fight.

She has so far not lost a single woman fighting Isis, a notoriously tough enemy, prompting critics to describe the unit as more propaganda than a real fighting force. Their base is more than an hour’s drive from the frontline, on the other side of the mountain. But Khider shrugs off the criticism as she describes manning a heavy machine gun during the fight to free Sinjar last autumn, under attack from Isis mortars and suicide bombers on motorbikes.

“I was in the front, I didn’t want them to fight without me,” she said, describing a position near the cement factory that is one of Sinjar’s landmarks. “Firing at Isis felt very encouraging.”

The battle was won, but the city is still an empty ruin today, with Isis only a few kilometres away, and Khider is frustrated about the lack of progress. The war is effectively on hold to allow forces to concentrate on the battle for Mosul, a few dozen kilometres away, but Khider thinks they should be part of that fight.

“We are disappointed, we keep asking them why are we not moving on this front,” she says. Ultimately, though, the singer who grew up steeped in the music of tragedy and resistance is convinced that her people will once more reclaim their homes. Yazidi tradition records more than 70 genocidal campaigns against them. Khider draws on these stories of survival and revenge to inspire her troops today, sharing the battle cries of men like Sheikh Mirza, who went to war more than a century ago to take down his brothers’ killer.

“If it was just for money, I wouldn’t leave Bashiqa and Barzan, my precious home villages, to come and fight you,” Khider says, reciting from memory, to a new generation of Yazidis hungry for vengeance. “I am coming to take revenge for my brothers, I will kill you and rip out your heart and liver. I am coming for you.”