The Isis leader, Abu Bakr al-Baghdadi, viewed women held captive at a Syrian house as his private property, and raped a number of them, including the American hostage Kayla Mueller.
As systematic rape becomes an increasingly powerful recruiting tool for Isis, the full story of the ordeal faced by the American aid worker, who would have turned 27 yesterday, is revealed by a 14-year-old Yazidi girl who was captured by Isis in Sinjar, Iraq, in August last year.
She says she spent around two months in captivity with Ms Mueller before escaping in October 2014.
After originally being held in the second Iraqi city of Mosul by Isis for little under a month, the 14-year-old and four other young Yazidi girls had, by late August of 2014, met Ms Mueller. They were then transferred to Al-Shadadiya, Syria.
According to the Yazidi girl, Ms Mueller had learnt basic Arabic while in captivity and went by the name of “Kayla Carol”. The last name derived from her father’s name – which in the Arab world serves as a family name – which is Carl.
Ms Mueller, an aid worker, had been kidnapped in Syria with her boyfriend in August of 2013 while leaving a Spanish Médécins Sans Frontières hospital in Aleppo. Isis had demanded a ransom of €5m (£3.2) for her release.
As a captive in Al-Shadadiya, Ms Mueller was often visited by the Isis leader. Rape was a reward for Isis victories. And, according to those held captive, many Yazidi women passed through the house on their way to being given as presents or sold to Isis fighters.
The Yazidi girl says the sex trade was organised by Umm Sayyaf, the Iraqi wife of Abu Sayyaf, a Tunisian Isis financier. She was captured in Syria in May by US Special forces and has reportedly been cooperating with US military interrogators. Last week, the White House announced that Umm Sayyaf would be prosecuted in Kurdish Iraq and would be “held accountable for her crimes”.
In the house in Al-Shadadiya, the four girls, all teenagers, were kept in one room with Ms Mueller, who tried to protect them from abuse and violence at the hands of Umm Sayyaf and Isis men, sometimes putting herself in greater danger by doing so.
Ms Mueller was described as a “mother figure”. But she left them regularly when Abu Bakr visited. The girls recognised him and other Isis leaders who came to the house.
Ms Mueller was taken to Abu Bakr’s room elsewhere in the house by Abu Sayyaf. “I saw him often; he came there often,” the Yazidi girl says. “And every time he came, he took Kayla away. She would always come back after.”
Every time she returned to the room Ms Mueller told the Yazidi girls what had happened, often crying, telling them that Abu Bakr had sexually abused her – or, in the conservative language the girl uses, that “he had married her by force”.
A source close to the Mueller family confirmed the story. The family is reportedly angry at claims that Ms Mueller had converted to Islam or had been a willing captive.