Mambo ya North Sudan/ South Sudan...
Sometimes you don't even need to divide the country physically.
Irak: shiha and suny
Lybia (and maghreb): Old regime/new regime
Afghanistan: Hata haieleweki tena nani against nani.
The only 'risk' of this method: it requires the consent of the victims.
the good thing about it: so far, no victim has opposed any resistance.