The events of August 1969 in Derry , and more particularly in Belfast where the IRA was unable to prevent loss of life or protect families burned out of their homes , brought to a head the divisions that had already appeared within the movement between the radicals and the traditionalists , and led to a split in December 1969 into the Official IRA and the Provisional IRA . Initially , both armies organised for defensive purposes only , although the Provisionals were planning towards an offensive campaign . In Derry there was far less hostility between the two organisations than elsewhere and householders commonly paid subscriptions to both . When rioters were arrested after the Official 's Easter parade in March 1970 , Officials and Provisionals picketed their trial together . At the start the Officials attracted most of the younger members . Martin McGuinness , who in August 1969 had helped defend the barricades , initially joined the Officials , but a few months later left to join the Provisionals .