Official IRA Belfast Brigade

The Official IRA's Belfast Brigade was founded in December 1969 after the Official IRA itself emerged in December 1969, shortly after the beginning of the Troubles, when the Irish Republican Army split into two factions. The other was the Provisional IRA. The "Officials" were Marxist-Leninists and worked to form a united front with other Irish communist groups, named the Irish National Liberation Front.

Source: Wikipedia — Official IRA Belfast Brigade (CC BY-SA 4.0)