The IRA, Northern Ireland's biggest republican paramilitary group, was founded nearly 80 years ago to fight for a united Ireland.
In 1969, the IRA split into the Official IRA and the Provisional IRA. The Official IRA took a more socialist line while the Provisionals, or Provos, became more militant, initially defending Catholics against loyalist attacks, then going on the offensive.
The Official IRA still exists, but when people now refer to the IRA, they nearly always mean the Provisional IRA.
The IRA declared a ceasefire in August 1994 following the Downing Street Declaration. This was broken by the Docklands bombing in early 1996, but restored in July 1997 - a move which allowed Sinn Fein to join the peace talks.
Unionists have alleged that this ceasefire has been broken, but the IRA has always insisted it is still in place.
The IRA only agrees with some aspects of the Good Friday Agreement, but many of its prisoners have been granted early release under the Agreement.
Following the Mitchell review of the peace process, the IRA appointed a go-between to deal with the decommissioning of terrorist weapons. No weapons were handed over by February 2000, however, leading to a political crisis and the suspension of the Assembly.
In May 2000, however, the IRA said it was ready to begin a process to put its weapons "completely and verifiably" beyond use.