On the eve of the First World War, the threat of civil war loomed in Ireland as Nationalists and Unionists has armed themselves and had established militant groups (the Irish Volunteers and the Ulster Volunteers respectively) in pursuit of their aims. The Ulster Covenant had already established the Unionist commitment to oppose Home Rule by any means necessary, which included force, and despite what nationalists continued to believe, Unionists were willing to use violence if it had to in order to prevent Home Rule.
It is generally agreed that the First World War had put a stop to the violence for a time as both nationalism and unionism were called upon to support the British war effort. A potential war was averted, ironically, by another larger war. By the end of the War, the rise of republicanism had swept away the support for Home Rule that had existed before the war and the question of devolution rather that outright independence became irrelevant.
What I am interested in is what might have happened had a civil war unfolded in Ireland (presuming that the war on mainland Europe had not taken place or had happened at a later date). I'm inclined to believe that Unionists might have succeeded in the war given the militarily superior Ulster Volunteers in comparison to the Irish Volunteers and the possible refusal of the British Army to engage after the Curragh incident. Of course, the Nationalists may have succeeded as well (although probably only with the support of the British Army), or the war might have had no decisive outcome and may have ended up back where it had started, or "status quo ante bellum". In the aftermath of such a war, the country might well have been partitioned or the very notion of home rule might have been dropped completely (even if the Nationalists had won), or it would have eventually been implemented (but probably being unable to govern properly in Ulster).
In any case, the war would have left the country devastated, and would probably have only enhanced the dire economic condition that Ireland was in at the time. Thousands would likely have been killed as a result and violence would likely have returned at a later date, as the war would probably have solved little politically.
We were lucky to have been spared of such a conflict (although the one which followed in Europe was undoubtedly far more tragic and damaging), but had it taken place, what do you feel would have been the outcome?