Izzadine Khader Khalif and Mahmoud Mardini sit cross-legged in the cramped tent for internally displaced persons (IDP), their pressed slacks, orderly moustaches, and clean-cut appearance a stark contrast to the exhausted faces that trudge up and down the damp, dreary IDP camp.

Khalif and Mardini have ­journeyed to the far north of Iraq to check up on Nawroz - a young Yazidi woman they rescued from the clutches of Islamic State (IS) slavery one month ago.

IS previously declared the ancient religion of the Yazidis a form of devil-worship - ultimately using this as justification for the capture and enslavement of an estimated 5000 Yaz-di women.

Nawroz is one of more than 150 people Khalif and Mardini have smuggled out of IS territory and into the relative safety of the Kurdish Autonomous Region of Iraq. The two men began their rescue campaign just three months ago, yet their secret web of contacts and safe houses now reaches across IS territory, from the self-proclaimed caliphate's capital in Raqqa, Syria, to Mosul, the militants' largest stronghold in Iraq.

In most cases, the cost of rescuing one person is about $4000 (£2500), Khalif explained to the Sunday Herald as he broke down the process. That money goes towards fake ID and documentation, new clothes, and to the contact on the inside. In order to smuggle the individual out, his home is used as a safe house and his family as a smokescreen, and he has to negotiate dozens of perilous IS checkpoints on this active frontline in one of the world's most dangerous warzones.

For the enslaved, their freedom is bought in some way - but Khalif and Mardini are secretive about the process, preferring to reiterate that money is paid to a contact on the inside who then sorts out the relevant transactions. As far as both men are concerned, they never directly make any payment to IS.

Sitting across from Nawroz, Khalif thumbs a bedraggled piece of paper with a list of names scrawled on it. The 151 names of the rescued, and the names of 73 others, almost all Yazidi women who are now slaves of the caliphate - are Khalif and Mardini's next targets.

Both men - Muslim Kurds who hail from Sinjar - have spent months struggling to piece back together Sinjar's broken families. Rescuing the kidnapped and enslaved has become a 24-hour obsession. They've made countless enemies in the process, their names now infamous in IS circles as they continually find ways of expanding their rescue network.

Nawroz's name appears halfway through their list. At just 18, she has seen every horror of war. She recounts her story with hesitance, breaking the narrative frequently to gather herself. Her smooth complexion tells of her youth, yet the heavy way her eyes seem stuck, emotionless and dull, tells of the terrors she has witnessed. She digs her nails into her hands as she speaks.

"I have the thoughts of everything that happened to me running through my head," she said, as she sat in the cold, muddy tent in which she and her husband now live. "My mind is sick," she murmurs. The signs of the physical abuse she endured have left her, but the mental scarring takes its devastating toll on the teenager every day.

On August 3, the IS surrounded Nawroz's hometown of Sinjar. 150,000 people fled. Men who were captured by the militants were rounded up and slaughtered in a set of genocidal massacres that took place against the Yazidi population. The estimated 5000 captured women were bundled into trucks and driven to IS strongholds - declared as "war prizes" and slaves of IS.

A SLAVE OF THE ISLAMIC STATE

Nawroz ran in panic as the militants entered Sinjar. Losing her husband amid the terrifying frenzy, she stopped and spun hoping to find him again. He was nowhere to be seen. The two men directly behind her were shot dead as she scanned the chaos.

Petrified, Nawroz froze. Within seconds she was grabbed by the militants and flung into the back of a lorry. As IS fighters paraded around her hometown, stalking out women to capture and hunting out men to kill, she was driven to IS-controlled Tal Afar near the Syrian border. Three days later she was taken to a prison in Mosul. Her enslavement and horrifying two-month ordeal had begun.

"Then they started to put us in groups," Nawroz recalled, as she attempted to regain her composure. Blood was beginning to show on her hands from crescent cuts caused by the pressing of fingernails into her skin.

"Old women were grouped together, young girls together, and they made a group of girls they thought were the prettiest. I was put in that group with 20 other girls. We were all sent to an IS barracks and then the fighters started to come. I was taken by an Emir [local Islamic State leader] as a slave after seven days there."

Khalif and Mardini said Nawroz's account of her capture was typical of what they have heard from other girls they have rescued - from the chaos before being captured, to the holding room full of girls waiting to be selected by IS fighters. Being chosen by an Emir, however, made her case particularly dire, they said.

Nawroz was forcibly married to the Emir straight away. Raped and beaten for eight days, she was then sold for $800 to the Emir's mother, who she believes took pity on her, buying her before the Emir could sell her off elsewhere.

With the images of the dead in Sinjar replaying in her mind, and her continued enslavement in Mosul, Nawroz gave up on ever seeing her family again.

One evening she heard the Emir and his mother talking about transferring her to Syria as a gift to fighters there. Nawroz ran to the kitchen to grab a knife so that she could kill herself.#

The Emir, realising, ran after her and stopped her. "After that the Emir's two sisters followed me everywhere," Nawroz continued. "Their job was to stop me from killing myself. I had thoughts of everything that had happened running through my head, the people I saw die. I was raped and beaten. He [the Emir] could do anything to me."

After two months as a slave, Nawroz found herself alone in a room for the first time during her ordeal.

The Emir's phone was lying on a table. She decided to lay her fears about her husband's fate to rest, frantically dialling his number with shaking hands. The phone rang twice, and was answered. Her husband, Fayez, was on the other end of the line, overwhelmed with relief when his wife's voice trembled out over the phone line.

Terrified of potential ramifications, Nawroz told her husband that he was never to call the number back. They said their goodbyes after one painful minute.

Unable to bear his wife's ­directions, Fayez phoned the number 10 days later and the Emir answered.

"He told me he was bored of her her and wanted $10,000," Fayez said, explaining the surreal conversation that resulted in negotiating a price to buy his wife from the IS leader.

"I went to everyone I knew, and ­eventually we got the money together from family," Fayez continued. "The money got to Mosul, and was given to the Emir through a friend I knew, but then we were stuck."

THE RESCUE

The task of ­smuggling Nawroz to safety appeared impossible. Is checkpoints would have to be negotiated, and she had no identification documents. She was stuck in Mosul, out of the Emir's iron grip but with no place to go, and one wrong step away from being enslaved again.

Fayez made frantic phone call after frantic phone call to no avail. At 4am the following morning, he was woken by the call that saved Nawroz's life.

A man identified himself to Fayez as Izzadine Khader Khalif. He said he knew the situation and could help. Khalif asked for every piece of information. Fayez complied.

"I heard about her case, and got in contact," Khalif recounted. "I had to be careful, I am a wanted man by the IS.

"I called my men on the other side [in Islamic State territory] and I told them to stake out the house where the girl was being hidden by her husband's friend. They staked it out for seven days, checked the whole back history of the story, and double-checked all phone numbers. After seven days, I gave the go-ahead for the rescue."

Khalif's men swung into action, taking Nawroz to one of their many safe houses in Mosul. In Nawroz's case, things had been simplified; the money had already been raised and transferred for her release, but the job was nowhere near over.

"She stayed in our safe house for one night," explained Mardini, sitting next to Khalif in the soggy IDP tent. "Khalif's guy made her a fake ID to say she was his daughter, he brought her clothes to blend in, and the next morning he brought his family and their car to the safe house - ready for the journey."

Mardini speaks softly compared to the more talkative and commanding Khalif. He has the aura of an intellectual and a planner, with an immaculate knack for attention to detail. Mardini was in Sinjar the day Nawroz was taken, helping to hide 80 people in his family home for seven nerve-wracking days before smuggling them out of the town under darkness, past the marauding militants, and to the relative safety of Sinjar Mountain.

The smuggling of people from under the radar of the IS has ­continued for Mardin. His goal, he says, is to help unshackle the 5000 women from Sinjar, like Nawroz, who were kidnapped and sold into slavery.

After just one night in Khalif and Mardini's safe house, Nawroz, with fake documents and new clothes, was piled into a small hatchback as the morning sun was rising over Mosul. Surrounded by her new "family", she endured 17 Islamic State checkpoints, before making it to Maktab Khaled checkpoint, a de-facto border crossing near Kirkuk between IS territory and Kurdish Peshmerga controlled Iraq.

As she walked through no-man's land, her husband Fayez's face began to appear in focus, his striking jet-black hair and kind eyes, features she thought she would never see again. Approaching the Peshmerga-controlled checkpoint, she saw two well-dressed men with warm smiles and neat, well-trimmed moustaches, speaking to Fayez and then turning to speak authoritatively with the armed and ready soldiers.

The Peshmerga let her straight through, and into her husband's arms. After two months as an IS slave, she was finally free.