Contemporary republicanism and the strategy of armed struggle

Assuming that the conflict of the past thirty years is now drawing to a close, we can, with a certain distance and detachment, attempt to map its parameters, examine its causes and consequences, and seek to learn from it. Why did the conflict initially break out, why did it last so long, and why did it end when it did? Has the Good Friday Agreement finally legitimated Northern Ireland as a political entity, and has violence now been de-legitimated as a weapon in Irish and in Irish-British politics? Is political violence likely to continue in some form and could it conceivably return on the scale of the past thirty years?