The Ustashi, the Croatian Fascists [largely Roman Catholic] are killing the Orthodox [mostly Orthodox] Serbs.
The Ustashi are the only people I’ve ever come across in my readings who were written up by the SS [in reports to Berlin] for brutality to prisoners-at least twice.
I don't profess to have much knowledge about the Ustashi but my general understanding has gone along the lines of it being first and foremost Croatian nationalist. A member of the Ustashi could be Catholic or Muslim. The leader, Ante Pavelic had a personal theology that was a syncretic mix of Islam and Catholicism.
“The Ustashi are the only people I’ve ever come across in my readings who were written up by the SS [in reports to Berlin] for brutality to prisoners-at least twice.”
Even Evil has standards...
http://tvtropes.org/pmwiki/pmwiki.php/Main/EvenEvilHasStandards