Northern Ireland: Current Issues and Ongoing Challenges in the Peace Process [Updated March 8, 2019] [open pdf - 1MB]
From the Document: "Between 1969 and 1999, almost 3,500 people died as a result of political violence in Northern Ireland, which is one of four component 'nations' of the United Kingdom (UK). The conflict, often referred to as 'the Troubles,' has its origins in the 1921 division of Ireland and has reflected a struggle between different national, cultural, and religious identities. Protestants in Northern Ireland (48%) largely define themselves as British and support remaining part of the UK ('unionists'). Most Catholics in Northern Ireland (45%) consider themselves Irish, and many desire a united Ireland ('nationalists')."
CRS Report for Congress, RS21333
Congressional Research Service: https://crsreports.congress.gov/