One of the most disturbing segments we've ever seen on The Project aired last night.

The Project features interviews with everyone from cancer survivors to viral internet stars, often touching on serious topics like illness, crime and death.

But we don’t think the show has ever featured a more raw – potentially distressing – segment than their interview with New York Times journalist Rukmini Callimachi.

Callimachi, creator of the podcast Caliphate, had reported from the Iraq city of Mosul when it was held by terrorist organisation Islamic State. But the award-winning foreign correspondent didn’t just report on the events, she spoke to IS’ members. And some of the insights she gained about the organisation are truly disturbing.

In a moment that seemingly left The Project audience stunned, Callimachi explained to host Hamish Macdonald how the IS recruits are taught to kill.

“It’s pretty gruesome. What is interesting about it, is ISIS recognises that it’s not easy to kill,” she began.

“ISIS recognises that in the end, this is perhaps the greatest human taboo.”

So, as Callimachi explained, the IS leaders would gradually work their new members up to murdering people in cold blood with a series of sinister steps.

“I have spoken to recruits who have described how they were put on kitchen duty. They were the ones who had to go outside, pick up the chicken and slaughter the chicken and cook the meal. Taking an animal life seems to be one of the first steps.”

Next, the reporter explained, they practice on dolls.

“The dolls are made to look quite realistic with ballistic shells inside of them. When they shoot them, they see the explosion of fake blood.”

And finally, they start to take human lives.

“Then the next step seems to be a group execution where they are made to line up in front of a number of executioners and together, they pull the trigger or they carry out the beheading.

“That is the step before you graduate to a solo execution. In the group execution, there is some level of anonymity. Everybody is doing it together. It’s almost a theatre that you are performing together.

“Doing it alone is of course harder.”

You find all the episodes of Rukmini Callimachi’s New York Times podcast Caliphate here.