The conflict began during a campaign to end discrimination against the Catholic/nationalist minority by the Protestant/unionist government and police force. The authorities attempted to suppress this protest campaign and were accused of police brutality; it was also met with violence from loyalists, who alleged it was a republican front. Increasing inter-communal violence, and conflict between nationalist youths and police, eventually led to riots in August 1969 and the deployment of British troops. Some Catholics initially welcomed the army as a more neutral force, but it soon came to be seen as hostile and biased. The emergence of armed paramilitary organisations led to the subsequent warfare over the next three decades.
The main participants in the Troubles were republican paramilitaries such as the Provisional Irish Republican Army (IRA) and the Irish National Liberation Army (INLA); loyalist paramilitaries such as the Ulster Volunteer Force (UVF) and Ulster Defence Association (UDA); British state security forces – the British Army and Royal Ulster Constabulary (RUC); and political activists and politicians. The security forces of the Republic played a smaller role. Republican paramilitaries carried out a guerrilla campaign against the British security forces, as well as a bombing campaign against infrastructure, commercial and political targets. Loyalists targeted republicans/nationalists, and attacked the wider Catholic community in what they claimed was retaliation. At times there were bouts of sectarian tit-for-tat violence. The British security forces undertook both a policing and a counter-insurgency role, primarily against republicans. There were some incidents of collusion between British security forces and loyalists. The Troubles also involved numerous riots, mass protests and acts of civil disobedience, and led to segregation and the creation of no-go areas.
More than 3,500 people were killed in the conflict, of whom 52% were civilians, 32% were members of the British security forces, and 16% were members of paramilitary groups. There has been sporadic violence since the Good Friday Agreement was signed, including a campaign by anti-ceasefire republicans.
A "peace line" in Belfast. The peace lines are a series of high barriers in Northern Ireland that separate nationalist and unionist neighbourhoods. They have been built at urban interface areas in Belfast, Derry, Portadown and elsewhere. The stated purpose of the peace lines is to minimise inter-communal violence.
The British government's position is that its forces were neutral in the conflict, trying to uphold law and order in Northern Ireland and the right of the people of Northern Ireland to democratic self-determination. Nationalists regard the state forces as forces of occupation or partisan combatants in the conflict. The British security forces focused on republican paramilitaries and activists, and the "Ballast" investigation by the Police Ombudsman confirmed that British forces colluded on several occasions with loyalist paramilitaries, were involved in murder, and furthermore obstructed the course of justice when claims of collusion and murder were investigated.
The Troubles were brought to an uneasy end by a peace process that included the declaration of ceasefires by most paramilitary organisations, the complete decommissioning of the IRA's weapons, the reform of the police, and the corresponding withdrawal of the British Army from the streets and sensitive Irish border areas such as South Armagh and Fermanagh, as agreed by the signatories to the Belfast Agreement (commonly known as the "Good Friday Agreement"). One part of the Agreement is that Northern Ireland will remain within the United Kingdom unless a majority of the Northern Irish electorate vote otherwise. It also established the Northern Ireland Executive, a devolved power-sharing government, which must consist of both unionist and nationalist parties.
Although the number of active participants was relatively small, the Troubles affected many in Northern Ireland on a daily basis; their impact sometimes spread to England and the Republic of Ireland, and, occasionally, to parts of mainland Europe.