(Reuters) - Here is a short history of the Northern Ireland conflict:
The seed of the conflict was planted in 1921 when the Anglo-Irish Treaty granted most of the island of Ireland autonomy from Britain, but maintained British rule over six northern counties with a large Protestant population.
In the late 1960s, tensions between Catholic Republicans and members of the pro-British Unionist majority spilled over into riots. British troops were deployed on the streets.
The Irish Republican Army (IRA), originally the name given to a militia that fought for Irish independence in the early part of the century, re-emerged. From 1972 onwards the splinter Provisional IRA took over the mantle of the armed struggle against British rule.
London took over direct rule of Northern Ireland in 1972, the bloodiest year of the "Troubles", when 467 people including 321 civilians were killed.
The IRA's support was dramatically boosted on January 30, 1972, when Catholics staged a peaceful but illegal protest in Londonderry, known to Republicans as Derry, against Britain's policy of imprisoning guerrilla suspects without trial.
British paratroopers shot dead 13 protesters on what became known as "Bloody Sunday". A 14th person died later.
In all, more than 3,600 people died in the conflict, including more than 1,000 members of the British security forces, and more than 36,000 were injured.
In a joint Anglo-Irish declaration in 1993, Britain said it would not block an end to British rule in Northern Ireland if a majority wanted it, and offered Sinn Fein a seat at peace talks if the IRA renounced violence. Talks followed.
The Good Friday Agreement, signed in April 1998, created a power-sharing assembly and government for Northern Ireland.
Disagreements over disarmament and the establishment of a new police service for the province brought suspensions, but devolved rule was definitively restored in 2007 when Protestant Unionist leader Ian Paisley and Sinn Fein's Martin McGuinness were sworn in as first minister and deputy first minister.
In 2010 a British judicial report into Bloody Sunday concluded that none of the victims had posed any threat to the soldiers and that their shooting was without justification. British Prime Minister David Cameron formally apologized for the killings.
(Reporting by David Cutler, London Editorial Reference Unit; Editing by Kevin Liffey)