Special Detective Unit
The Special Detective Unit (SDU) () is the main domestic security agency of the Garda Síochána, the national police force of Ireland, under the aegis of the Crime & Security Branch (CSB). It is the primary counter-terrorism and counter-espionage investigative unit within the state. The Special Detective Unit superseded the Special Branch (which they are still commonly referred to as), which itself replaced the older Criminal Investigation Department (CID), which was founded in 1921. They work in conjunction with the Defence Forces Directorate of Military Intelligence (J2) – Ireland's national intelligence service – on internal matters. The unit's headquarters are in Harcourt Street, Dublin City. The Emergency Response Unit (ERU), a specialist armed tactical unit, was a division of the SDU until 2017 when the Special Tactics and Operational Command took over command of the unit. History The Civic Guard was formed by the Provisional Government in February 1922 to take over the responsibility of policing the fledgling Irish Free State. The Garda Síochána (Temporary Provisions) Act 1923 enacted after the creation of the Irish Free State on 8 August 1923, provided for the creation of "a force of police to be called and known as 'The . Separate from