(CNN)Here's a look at Northern Ireland. For many years, Northern Ireland has been split over the question of whether it should remain part of the United Kingdom or become part of Ireland.
Northern Ireland's history has been marked by sectarian violence, although in recent years, its political parties have been working toward compromise, and the two sides now make up a power-sharing government. Nationalists prefer to belong to a single, united Ireland. Unionists prefer to remain a part of the UK.
The Democratic Unionist Party (DUP)
Formed in 1971 by Ian Paisley, a Protestant preacher. Historically, it has attracted support from working-class Protestants.
The party attracts middle-class Catholic support and aims to achieve the reunification of Ireland through democratic means.
Advocates a united Ireland free from British rule or a British presence.
Founded in 1919 as a paramilitary group fighting for an independent Ireland. In 1969, the IRA split into the Official IRA and the Provisional IRA (the former rejected violence while the latter favored being an armed force). In 2005, the Provisional IRA announced that its military campaign was over and its weapons would be scrapped.
1920 - The Government of Ireland Act splits the country into two separate political units, with Belfast as the capital of the north and Dublin as the capital of the south.