09 August 1971,
The British army killed 11 civilians in cold blood in 36 hours. The army launched what they called operation Demetrius. 3,000 soldiers entered northern Ireland and arrested 346 people to imprison them without trial. It has subsequently been shown that most detainees did not belong to the IRA.
The police operation provoked an immediate response among the Irish Republicans and caused great disturbances. The political conflict was hardened.
On Monday, 9 August 1971, the 600 British soldiers welcomed the West Belfast area of Ballymurphy, entering the homes and bringing the men detained. Young and old, they shot those who resisted leaving the house.
The British Parachute Regiment killed 11 civilians.
Source:
Luis Antonio Sierra, Northern Ireland: History of the conflict (Silonia).