Around 2016, there was some profiling of the UK citizens that had joined Isis. A third of them had convictions for rape, sexual violence and robbery. Another significant tranche of them had been violent, controlling and abusive to wives - although there had been few convictions because their wives and families had been silenced. They could only reveal their sadism once the ISIS recruits had left this country.
A report by the Henry Jackson society (2018), reported in the Guardian, said (extract):
Men with a history of sexual violence and domestic abuse joined Islamic State because of the organisation’s systemic use of rape and slavery as a form of terrorism.
The promotion and sanctioning of sexual violence by the extremist group was a pivotal means of “attracting, retaining, mobilising and rewarding fighters” as well as punishing kaffir, or disbelievers
Article: Rape and Slavery was Lure for UK ISIS Recruits with History of Sexual Violence
www.theguardian.com/world/2017/oct/07/isis-rape-slavery-british-recruits-islamic-state