Operation Demetrius (or internment, as it was known) began at 4.30am on Monday 9 August 1971, when the British Army began arresting those identified by the RUC. Of the 342 men arrested, 116 were released within 48 hours. Some 226 men were detained: 86 from Belfast, 60 from County Derry, 20 from the Newry area, 20 from Armagh and 40 from Fermanagh and Tyrone. Internment continued until 5 December 1975. During that time 1,981 people were detained; 1,874 were Catholic/republican, while 107 were Protestant/loyalist. Shortly after the first arrests, many internees were held in an internment camp built on a disused RAF base at Long Kesh near Lisburn, Co. Antrim. Of the 160 men in Crumlin Road prison, no more than 80 had anything to do with the IRA, and of these only four were senior officers (none of them the top men). The rest of the internees were political opponents of the Unionists—like People’s Democracy and Northern Ireland Civil Rights Association members, old retired IRA ex-internees, militant trade unionists, public speakers and, in some cases, people held on mistaken identity.