Operation Demetrius was a British Army operation in Northern Ireland on 9–10 August 1971, during the Troubles. It involved the mass arrest and internment of people suspected of being involved with the Irish Republican Army (IRA), which was waging an armed campaign for a united Ireland against the British state. It was proposed by the Unionist government of Northern Ireland and approved by the British Government. Armed soldiers launched dawn raids throughout Northern Ireland and arrested 342 in the initial sweep, sparking four days of violence in which 20 civilians, two IRA members and two British soldiers were killed. All of those arrested were Irish republicans and nationalists, the vast majority of them Catholics. Due to faulty and out-of-date intelligence, many were no longer involved in republican militancy or never had links with the IRA. Ulster loyalist paramilitaries were also carrying out acts of violence, which were mainly directed against Catholics and Irish nationalists, but no loyalists were included in the sweep.

Bloody Sunday, or the Bogside Massacre, was a massacre on 30 January 1972 when British soldiers shot 26 unarmed civilians during a protest march in the Bogside area of Derry, Northern Ireland. Thirteen men were killed outright and the death of another man four months later was attributed to gunshot injuries from the incident. Many of the victims were shot while fleeing from the soldiers, and some were shot while trying to help the wounded. Other protesters were injured by shrapnel, rubber bullets, or batons, two were run down by British Army vehicles, and some were beaten. All of those shot were Catholics. The march had been organised by the Northern Ireland Civil Rights Association (NICRA) to protest against internment without trial. The soldiers were from the 1st Battalion of the Parachute Regiment, the same battalion implicated in the Ballymurphy massacre several months before.