the roots of their war are territorial wishes. The protestants were rebelled against the English (catholic or anglicanic) garrison - that's way Northern Ireland still is independent. During that rebellion the catholics in the protestant area really had to fear for their life (like still today) and took revenge on the protestants in Southern Ireland which is mostly catholic.
The conflict between these two fractions lead to prejudices and private feuds that ended in the conflict as it is today.

The independence of Northern Ireland is still not accepted by the catholics, and the protestants want it to be officially promised by them. That's the origin of their problems.

Please correct me if I'm wrong.

perpeduumimmobile