A member loyal to the Islamic State in Iraq and Syria (ISIS) waves an ISIS flag in Raqqa. (Reuters / Stringer)

No sooner am I settled in an interviewing room in the police station of Kirkuk, Iraq, than the first prisoner I am there to see is brought in, flanked by two policemen and in handcuffs. I awkwardly rise, unsure of the etiquette involved in interviewing an ISIS fighter who is facing the death penalty. He is small, much smaller than I, on first appearances just a boy in trouble with the police, his eyes fixed on the floor, his face a mask. We all sit on armchairs lined up against facing walls, in a room cloudy with cigarette smoke and lit by fluorescent strip lighting, a room so small that my knees almost touch the prisoner's—but he still doesn't look up. I have interviewed plenty of soldiers on the other side of this fight, mostly from the Kurdish forces (known as pesh merga) but also fighters in the Iraqi army (known as the Iraqi Security Forces or ISF), both Arab and Kurdish. ISIS fighters, of course, are far more elusive, unless you are traveling to the Islamic State itself, but I prefer to keep my head on my shoulders.

Rumors abound as to summary executions of ISIS prisoners without due process, but of course no one will go on the record to report such abuses of human rights. Anecdotally, we were told about a prisoner who was interrogated for 30 days but only said "Allahu Akbar" (God is great) for the entire month. "Wouldn't you shoot him?" they asked. One peshmerga gave an eyewitness report about five prisoners captured, questioned, and shot in the head. We spoke to various military leaders who said they didn't want to take prisoners, since injured bodies are often booby-trapped and kill approaching soldiers; for this reason the PKK has a take-no-prisoners policy. (The PKK, or Kurdistan Workers' Party, is the Kurdish separatist group based in Turkey and northern Iraq that is on the international terrorism list; in proving themselves indispensable in the fight against ISIS, they have caused a dilemma for Western governments. They are seemingly not so indispensable that those governments have felt compelled to oppose Turkey's recent bombing campaign against them.)

Another source told us of the futility of holding prisoners for their bargaining power: "With ISIS, there's no compromise, no negotiation…they're not interested in prisoner exchange because they believe that they're better off dead." Whatever the truth of the behavior of the military and security services, the fact remains: ISIS prisoners are hard to find.

One evening we watch a documentary on BBC Arabic profiling Brig. Gen. Sarhad Qadir, the head of police in the Iraqi governorate of Kirkuk. He is shown policing the town of Kirkuk, personally patrolling the streets and houses, arresting people suspected of fighting for ISIS. Kirkuk, then, seems like a good place to start: At least there are prisoners there, shown by the BBC, no less.

And so my colleagues and I drive to Kirkuk from the capital of Iraqi Kurdistan, Erbil, to meet Qadir. Despite the workload of maintaining security in this uneasy city of mixed ethnicity (mostly Arab, Kurdish, and Turkmen), rife with ISIS sleeper cells, he is welcoming, sending armed guards to bring us in from the highway to the city. We are served tea in his office, and he sits with us for half an hour before we are taken to the interview room with two colonels. (The week after I left the country he and other officers would be caught in a huge car bomb; Qadir was wounded for the fourteenth time in the service of Kurdistan.)