Quote Originally Posted by Don Corleone
-Now, there were two factions in the early ROI: there were those who believed in the compromise (under Michael Collins) and those who believed the entire island must move as one (Eamon DeValera's gang), all stay or all leave, and to them, it was all leave. And upon the declaration of the formation of the ROI, Ireland began it's first days of independence with a terrible, bloody, vicious civil war that pitted friends against friends, and literally brothers against brothers. The English actually played almost no role in this, this was Irish Catholic Republicans killing Irish Catholic Republicans. In the end, De Valera's side won, mainly due to the death of Michael Collins. There's some speculation that De Valera arranged for Collin's murder under the auspices of a peace negotation, but the evidence either way just isn't there. My point is, the Irish were fighting themselves from the get go over the issue of Ulster, and there's plenty of blame to be laid on both sides, Hollywood's opinion aside. However, the ROI adopted an official policy of seeking unification with Ulster. They were not however prepared to take military action to see it happen, they mainly sat back and made some strongly worded statements occassionally, usually come election time.
If i remember correctly, the opposants to the partition lost the civil war and Collin's side won it. De Valera was latter elected president but this had nothing to do with civil war.