In early August, the Yazidi diaspora in the United States and Europe began to receive hundreds of calls from terrified calls from back home, around Mount Sinjar. Desperate relatives were ringing in droves, asking for help, guidance, or just to be on the phone with their loved ones as death approached (one of my fellow Yazidis in Houston had to field just such a call).

The reason for their terror soon became clear. Isis were approaching from all four directions around the besieged rock of Sinjar. People were retreating in a desperate melee, people hopping on every wheeled vehicle their could operate, from dump trucks to small cars, front loaders to old backyard stalled cars.

Luckily, most of the people of Khanasor, my hometown, were able to leave before IS's bloodthirsty gunmen reached the town. But the situation in other towns dotted north and south of Sinjar was far more difficult; the two towns most badly affected were Kocho and Hatimia, which were besieged and overrun before anyone was able to escape.

When IS arrived in towns like Kocho and Hatimia, they often went street to street, killing any Yazidi men over the age of 15 or 16 they came across, and throwing women and children on trucks. Within a few days of the attack, IS had cleansed most of the Yazidi villages of life.

The Sinjar Crisis Group, a collection of Yazidi activists I helped form in the aftermath of the attack, estimates that between 5,000 and 7,000 Yazidis, mostly women and children, were abducted during this period. I have heard some harrowing tales; one 75-year-old from Khanasor told me that a militant had pushed her from a speeding truck, saying that IS would rather leave her to a slow death on the open ground than waste bullets on her. That old woman walked for two days and nights, until she reached safety and was rescued by the Yazidi defenders.

Yet perhaps an even more horrific tale is told by Samia, a woman I met in January during a trip to Iraq. Samia was taken captive in Kocho in August; I met her in a wealthy home, which took her in after she and her 19-year-old sister, Sanaa, managed to escape the IS captors. Her story shows IS in all its depraved brutality, particularly given she is battling a terminal illness.

'There was unity, compassion, and love'

Samia is from a family of five - two sisters and one brother. She told me that, before IS came, her family was poor, but happy. Kocho was a farming village, "but people started to work after the Iraqi freedom operation in 2003, they started to send their children to school, there was a sense of unity in the village, compassion, and love."

Samia got married in January 2009 to a man from a nearby village, and had a happy life with her support network in Kocho. But after a 2007 Al-Qaeda incursion killed about 1,000 people in two Yazidi towns, Samia says she "always lived with fear that something bad will happen. My guts were telling me that some evil is looming, every night I prayed that the village will be safe and my family will be safe."

That same year Samia was diagnosed with cancer. Her family spent all they had on her treatment, her brothers and parents grafting on farms and construction sites to pay for her medication. She was still undergoing chemotherapy in August 2014, when Kocho was surrounded by IS militants and she was taken captive.

'After being kidnapped in Sinjar, the Yazidi boys and girls were taken away by force from their mothers and "distributed among houses" in Mosul and Tal Afar, where they stayed for a total of five months.' Read Gianluca Mezzofiore's analysis of the Yazidi ordeal here.

"We were waiting for the airstrikes to take place so we can escape" she told me, "but they never came. One night, IS members came to the village and told us 'you will have to convert to Islam or die.'

"The chief of the village asked for some time to think about a deal, he said I would have to consult others in the village; IS gave the Yazidis two days to declare their [support for] Islam."

After just a single night had elapsed, an IS Amir came to the village and told the villagers they had two choices: convert to Islam if they wished to stay in their village, or leave if they wished to preserve their freedom. The villagers wanted the freedom, but this was nothing but a trick.

Late on the evening of 15 August, IS put the villagers in the local school; women and children on the second floor and the men on the first.

"While in the school, IS stripped everyone from their belongings, they threatened us with death if we don't give away our belongings" Samia says. "They took the gold and money first, and then they took our cellphones. That is when we realised something bad was happening."

Shot and dumped in mass graves

The men were taken out of the village in four separate groups by truck. Samia and other women and children heard shots coming from the distance.

"From that moment, the images of my father disappeared. They loaded them in the trucks, after a short time we heard the shots, we asked them what they are shooting at, they said they were shooting the dogs."

The testimony of the handful of survivors, and satellite imagery, indicates that those men were killed en masse. A total of 418 Yazidi men were killed in just a few moments in trenches around Kocho. The mass graves have yet to be discovered; Samia's father, and her brother, remain unaccounted for.

The women and children were taken to a nearby building. Samia, her sisters and eight other girls were loaded in a truck, part of a convoy of around 130 young females headed for Mosul.

\'They loaded the men in the trucks, after a short time we heard the shots, we asked them what they are shooting at, they said they were shooting the dogs.\'

"On our way, the IS driver said we should have accepted Islam, they said we should have converted to avoid all this" said Samia, before adding that the strength of the villagers' faith meant this would never have been an option.

Some were denied even the ignominy of being hauled onto a truck and driven away. The elderly women in the Kocho school, including Samia's mother, were taken into the garden; Samia has never seen her mother since she was taken. Again, it is claimed by eyewitnesses who managed to escape that the old women were massacred and buried in a mass grave.

When the girls got to Mosul, IS took the remaining of Samia's belongings; they even took her cancer medication. Naturally, the cellphone was seized, although Samia recalls that "I put the sim card I had under my tongue, my sister also had a sim card that she was able to hide." The Sim cards were later used to connect them with family members during their escape.

'Even tears were punished with a beating'

Samia, her two sisters, and 32 Yazidi women and girls were eventually given as a present to IS's Wali (chief) of Mosul, Haji Shaker. "The Wali received us at his residence [in the IS camp] and told us that we are his share. Four more Yazidi women were at his residence when we arrived"

Samia and her two sisters did not eat for six days and wanted to cry for their fate. But an IS henchman, guarding them in the house, had a chain in his hand and promised to beat whoever cried. "Even tears were forbidden" says Samia.

One day, Samia and the other girls were asked to take a shower. They knew this would mean sexual assault and planned to resist; however, an IS gunman with a whip in his hand forced them to do it.

In the night a man came to the house, checking the girls one by one by examining their faces with a torch.

"It was my sisters turn, the gunman wanted to check my little sister's face," Samia recalls. "Sanaa put her head down, but the gunman pulled her by her hair and hit her face with the flashlight.

"We cried, we begged them to leave my sister alone, and finally the man moved on to another girl. The other girl was also from Kocho in her 15, she was beaten up with the whip and dragged down the stairs from her hair.

"We were very scared, we were crying and screaming, they were beating us up every time we cried, they were insulting us, insulting our faith."

'While IS is undoubtedly taking ground in Anbar – a majority Sunni area that has long been associated with violent insurgency and was one of the terror group's first strongholds in Iraq – experts say that the Iraqi Security Forces remain in control of key buildings, including the Iraqi Army Brigade HQ, Anbar Operational Command Centre and the city government complex.' Orlando Crowcroft analyses the offensive against Isis in Iraq. Read here.

Samia's middle sister, Sara, was taken to another house, while her youngest sister, Sanaa, was kept by the Wali as his slave. After only two days, Sanaa attempted to escape, stealing the Wali's wife's phone and walking through the streets of Mosul seeking help. The attempt was unsuccessful and Sanaa was captured by IS militants, along with a Sunni man who tried to shield her in his house.

"My sister was beaten up so bad, she could not walk for 20 days" Samia recalls. "She was beaten up by two IS militants, her body was covered with marks and blood, and she was put alone in a room for two days without food or water."

All the Yazidi girls in the Wali's house were eventually gifted to militants as presents, one by one.

"A Yazidi child of age of 13 and another one of age of 15 were taken upstairs, they were both raped, we listened to them shouting and crying. We were powerless, we were hopeless, we could not stop the rape" says Samia.

"An IS member, named Abu Yahya, who was in his late 30s, he came and wanted to take my sister Sara, he came in the evening and then came in the morning again, we resisted and he beat up my sister, my sister was really suffering."

Samia herself was the property of a militant known as Abu Ahmed. She played with him that she was on cancer medication, telling him "I'd had chemo treatment and my husband and I had not had sex for three years because of my condition, because I could not get pregnant."

These pleas went unheeded. Samia was raped multiple times by Abu Ahmed; in fact she was forced to have sex every time he came back from battle, as a kind of trophy, a reward for his efforts in the field.

During this hellish 25-day stay, Samia made one desperate bid to escape. As a militant approached her, she tried to pull out his pistol. But she was not strong enough to take the hun, and three strong militants quickly pinned her down.

'We tied a scarf to the window and slid towards freedom'

But, despite the horror, Samia's spirit remained. One night she, her sister Sanaa, and another girl, aged 15, decided to escape. Although the Wali's house was well-fortified, they felt they could flee for safety by donning black Islamic dresses, as well as a little food and water.

"We tried to get out through the windows, the window was too small" says Samia. "Then we tried through a door, we broke the inner lock but the door was locked from the outside. Finally we found a window that we could fit in, we tied a scarf to the frame and slid from the second floor to an annex room."

The three terrified girls walked for five blocks and hid in an abandoned building. They stayed inside the abandoned building for two days; whilst there, they donned the Islamic dress and managed to call a Yazidi activist in Dohuk.

The activist managed to find someone in Mosul who connected with the girls, picked them up from the location and took them to his house. Then he drove them a village near the Kurdistan border, given them directions for a six-hour journey to reconnect with their family. Samia's husband was at the border, waiting, when she arrived.

Samia struggled for several months after coming back from captivity. She resumed cancer treatment, but she also suffered from trauma and suffered seizures on an almost daily basis. In fact, during our chat she suffered a seizure, blacking out and falling to the floor in the middle of the conversation.

After speaking to me, she went to Germany for treatment and resettlement through a programme established by the German government. However, her husband has remained in Iraq, and has enlisted to fight against IS.

Throughout this eight-month nightmare, Samia has been sustained by the hope that her mother, father and brother are still alive. "No one has seen them dead, we hope they are alive, we have to hope, we will wait for them forever" she says.

I have met hundreds of families who lived exactly as Samia and her two sisters. Despite the unimaginable turmoil they have been through, they are driven on by hope, hope that their relatives will come back one day.

Murad Ismael works for Yazda, an NGO set up to help the Yazidi people and raise awareness of Isis's crimes against them. Visit www.yazda.org or follow the group on Twitter @Yezdaorg.