Royal Ulster Constabulary in the context of "Militarization of police"

The Provisional Irish Republican Army (Provisional IRA), officially known as the Irish Republican Army (IRA; Irish: Óglaigh na hÉireann) and informally known as the Provos, was an Irish republican paramilitary force that sought to end British rule in Northern Ireland, facilitate Irish reunification and bring about an independent republic encompassing all of Ireland. It was the most active republican paramilitary group during the Troubles. It argued that the all-island Irish Republic continued to exist, and it saw itself as that state's army, the sole legitimate successor to the original IRA from the Irish War of Independence. It was designated a terrorist organisation in the United Kingdom and an unlawful organisation in the Republic of Ireland, both of whose authority it rejected.

The Provisional IRA emerged in December 1969, due to a split within the previous incarnation of the IRA and the broader Irish republican movement. It was initially the minority faction in the split compared to the Official IRA but became the dominant faction by 1972. The Troubles had begun shortly before when a largely Catholic, nonviolent civil rights campaign was met with violence from both Ulster loyalists and the Royal Ulster Constabulary (RUC), culminating in the August 1969 riots and deployment of British soldiers. The IRA initially focused on defence of Catholic areas, but it began an offensive campaign in 1970 that was aided by external sources, including Irish diaspora communities within the Anglosphere, and the Palestine Liberation Organization and Libyan leader Muammar Gaddafi. It used guerrilla tactics against the British Army and RUC in both rural and urban areas, and carried out a bombing campaign in Northern Ireland and England against military, political and economic targets, and British military targets in mainland Europe. They also targeted civilian contractors to the British security forces. The IRA's armed campaign, primarily in Northern Ireland but also in England and mainland Europe, killed over 1,700 people, including roughly 1,000 members of the British security forces and 500–644 civilians.

During 12–16 August 1969, there was an outbreak of political and sectarian violence throughout Northern Ireland, which is often seen as the beginning of the thirty-year conflict known as the Troubles. There had been sporadic violence throughout the year arising out of the Northern Ireland civil rights campaign, which demanded an end to discrimination against Catholics and Irish nationalists. Civil rights marches had been attacked by Protestant loyalists, and protesters often clashed with the Royal Ulster Constabulary (RUC), the overwhelmingly Protestant police force.

On 12 August, the Battle of the Bogside erupted in Derry: three days of fierce clashes between the RUC and thousands of Catholic/nationalist residents of Derry's Bogside district. The besieged residents built barricades and set up first aid posts and workshops for making petrol bombs. Police fired CS gas at rioters for the first time in the history of the UK. In support of the Bogsiders, on 13 August Catholics/nationalists held protests elsewhere in Northern Ireland, some of which led to violence. The bloodiest clashes were in Belfast, where seven people were killed and hundreds wounded, five of them Catholic civilians shot by police. Protesters clashed with both the police and with loyalists, who attacked Catholic districts. Scores of homes and businesses were burnt out, most of them owned by Catholics, and thousands of mostly Catholic families were driven from their homes. In some cases, police helped the loyalists and failed to protect Catholic areas. Both republican and loyalist paramilitaries were involved in the clashes. There were also clashes between protesters and police in Armagh, where a protester was killed by police, as well as in Dungannon and Newry.

Operation Banner was the operational name for the British Armed Forces' operation in Northern Ireland from 1969 to 2007, as part of the Troubles. It was the longest continuous deployment in British military history. The British Army was initially deployed, at the request of the unionist government of Northern Ireland, in response to the August 1969 riots. Its role was to support the Royal Ulster Constabulary (RUC) and to assert the authority of the British government in Northern Ireland. This involved counter-insurgency and supporting the police in carrying out internal security duties such as guarding key points, mounting checkpoints and patrols, carrying out raids and searches, riot control and bomb disposal. More than 300,000 soldiers served in Operation Banner. At the peak of the operation in the 1970s, about 21,000 British troops were deployed, most of them from Great Britain. As part of the operation, a new locally-recruited regiment was also formed: the Ulster Defence Regiment (UDR).

The Provisional Irish Republican Army (IRA) waged a guerrilla campaign against the British military from 1970 to 1997. Catholics welcomed the troops when they first arrived, because they saw the RUC as sectarian, but Catholic hostility to the British military's deployment grew after incidents such as the Falls Curfew (1970), Operation Demetrius (1971) and Bloody Sunday (1972). In their efforts to defeat the IRA, there were incidents of collusion between British soldiers and Ulster loyalist paramilitaries. From the late 1970s the British government adopted a policy of "Ulsterisation", which meant giving a greater role to local forces: the UDR and RUC. After the Good Friday Agreement in 1998, the operation was gradually scaled down, most military facilities were removed and the vast majority of British troops were withdrawn.

The Police Service of Northern Ireland (PSNI; Irish: Seirbhís Póilíneachta Thuaisceart Éireann; Ulster Scots: Polis Service o Norlin Airlan), is the police service responsible for law enforcement and the prevention of crime within Northern Ireland.

It is the successor to the Royal Ulster Constabulary (RUC) after it was reformed and renamed in 2001 on the recommendation of the Patten Report.