They were first used in Northern Ireland in 1971 as part of Operation Demetrius – the mass arrest and internment (imprisonment without trial) of people suspected of involvement with the Irish Republican Army (IRA). Out of those arrested, fourteen were subjected to a programme of "deep interrogation" using the five techniques. This took place at Shackleton Barracks, a secret interrogation centre in Northern Ireland. For seven days, when not being interrogated, the detainees were kept hooded and handcuffed in a cold cell and subjected to a continuous loud hissing noise. Here they were forced to stand in a stress position for many hours and were deprived of sleep, food and drink. They were also repeatedly beaten, and some reported being kicked in the genitals, having their heads banged against walls and being threatened with injections. The effect was prolonged pain, physical and mental exhaustion, severe anxiety, depression, hallucinations, disorientation and repeated loss of consciousness. It also resulted in long-term psychological trauma. The fourteen became known as "the Hooded Men" and were the only detainees in Northern Ireland subjected to all five techniques together. Other detainees were subjected to at least one of the five techniques along with other interrogation methods.