From Wikipedia

Brits Part 1 - Secret War

The Troubles
(Irish: Na Trioblóidí)
was a period of ethno-political conflict in Northern Ireland which spilled over at various times into England, the Republic of Ireland, and mainland Europe. The duration of the Troubles is conventionally dated from the late 1960s and considered by many to have ended with the Belfast "Good Friday" Agreement of 1998. Violence nonetheless continues on a sporadic basis.

The principal issues at stake in the Troubles were the constitutional status of Northern Ireland and the relationship between the mainly-Protestant unionist and mainly-Catholic nationalist communities in Northern Ireland. The Troubles had both political and military (or paramilitary) dimensions. Its participants included politicians and political activists on both sides, republican and loyalist paramilitaries, and the security forces of the United Kingdom and of the Republic of Ireland.