So, you know what the IRA is. How about the CIRA? ORM? INLA? IPLO? Over the last 30 years there have been quite a number of republican paramilitary groups active in Northern Ireland, not to mention the various other "flags of convenience" that these groups have sometimes used. The common ancestor of all these groups is the IRA of the late 1960s; numerous splits and feuds since then have given birth to these different groups, some of which are still around and some of which are not.
The first split, and probably the biggest, was the one that took place in 1969. This was when the pogroms against Catholics in the north broke out as the Civil Rights movement was smashed, and many of the victims complained bitterly that the IRA had failed to defend them (graffiti that appeared reading "IRA = I Ran Away" summed up the feeling of the time). Many of the IRA members in the north broke away from the organization and formed the Provisional IRA, attracting hundreds of recruits who were eager to defend their communities (membership peaked at around 1,500 in 1972). The Provisionals, or Provos, were much more militant and soon outnumbered their old comrades who were now known as the Official IRA.
Those who remained in the Official IRA took a dim view of the Provos, regarding them as apolitical and dubbing them the "Rosary Bead Brigade". There was a lot of truth in this view, for while the Official IRA was ideologically-motivated and moving in a Marxist direction, the Provisionals were motivated by more practical concerns such as defending their streets and homes. Many of those who joined were in fact conservative Catholics, and they were far from being the sort of political radicals who made up the Officials. Not that there weren't any political radicals who defected to the Provisionals, there were, they were just in a minority.
The Officials continued transforming themselves into a reformist, leftist political organization, and in 1972 declared a permanent ceasefire. Not everyone within the organization agreed with ending the armed struggle against British rule in Northern Ireland, and led by Seamus Costello they left to form the Irish National Liberation Army (INLA). Joining the Provisionals was not viewed as an option, because they were viewed as too conservative and, well, too Catholic. The INLA was formed to be an avowedly socialist, non-sectarian group made up of both Catholic and Protestant workers who saw that Britain's hold of Northern Ireland was not in the interests of either section of the Irish working class.
