Inside the Secret Rescue of Sex Slaves From ISIS

'This kind of operation can't be done during daytime. We are basically going in there to kidnap them back from ISIS,' mission leader Khaleel Al-Dhaki told NBC News.

'Saving a soul is the best thing a man can do,' said Al-Dhaki 'You get more motivated when you watch them meeting their families. I can't describe the moment of the reunion. We devote our whole lives to rescuing these women.'

Al-Dhaki estimates ISIS has kidnapped around 7,000 Yazidis and that roughly 3,000 of them managed to escape on their own or were ransomed out of bondage. The fate of 1,000 Yazidi men remains unknown.