Flannery edits the Dominican bi-monthly journal entitled Doctrine and Life from 1958 to 1988, while at St. Saviour’s Priory, Dublin, where he also serves as prior from 1957 to 1960. He also edits the Religious Life Review. He publishes many English language documents on the Second Vatican Council.
O’Riordan joins the Communist Party of Ireland in 1935 while still in the IRA and works on the communist newspaper The Irish Workers’ Voice. In 1937, following the urgings of Peadar O’Donnell, several hundred Irishmen, mostly IRA or ex-IRA men, go to fight for the Spanish Republic in the Spanish Civil War with the XVth International Brigade. They are motivated in part by enmity towards the 800 or so Blueshirts, led by Eoin O’Duffy who go to Spain to fight on the “nationalist” side in the Irish Brigade. He accompanies a party led by Frank Ryan. In the Republic’s final offensive of July 25, 1938, he carries the flag of Catalonia across the River Ebro. On August 1, he is severely injured by shrapnel on the Ebro front. He is repatriated to Ireland the following month, after the International Brigades are disbanded.
In 1938 O’Riordan is offered an Irish Army commission by the Irish Free State but chooses instead to train IRA units in Cork. As a result of his IRA activities during World War II, or the Emergency as it is known in neutral Ireland, he is interned in the Curragh internment camp from 1939 until 1943 where he is Officer Commanding of the Cork Hut and partakes in Máirtín Ó Cadhain’s Gaelic League classes as well as publishing Splannc (Irish for “Spark,” named after Vladimir Lenin‘s newspaper).
In 1944 O’Riordan is founding secretary of the Liam Mellows Branch of the Labour Party and in 1945 is a founding secretary of the Cork Socialist Party, whose other notable members include Derry Kelleher, Kevin Neville and Máire Keohane-Sheehan.
In 1947, O’Riordan is a founding secretary of the Irish Workers’ League and general secretary thereafter, and of its successor organisation the Irish Workers’ Party from 1962–70.
In all O’Riordan runs for election five times, campaigning throughout for the establishment of a socialist republic in Ireland but given Ireland’s Catholic conservatism and fear of communism, he does so without success. He does, however, receive playwright Sean O’Casey‘s endorsement in 1951.
O’Riordan’s participation in the Spanish Civil War is always an important part of his political identity. In 1966 he attends the International Brigades’ Reunion in Berlin and is instrumental in having Frank Ryan’s remains repatriated from Germany to Ireland in 1979.
O’Riordan is a member of the Irish Chile Solidarity Committee and attends the 1st Party Congress of the Communist Party of Cuba in 1984. He also campaigns on behalf of the Birmingham Six and attends their Appeal trial in 1990. He serves as General Secretary of the Communist Party of Ireland (1970–83) and as National Chairman of the party (1983–88). He publishes many articles under the auspices of the CPI.
O’Riordan’s last major public outing comes in 2005 at the re-dedication of the memorial outside Dublin’s Liberty Hall to the Irish veterans of the Spanish Civil War. He and other veterans are received by President of IrelandMary McAleese. He is also presented with Cuba’s Medal of Friendship by the Cuban Consul Teresita Trujillo to Ireland on behalf of Cuban President Fidel Castro.
In 1969, according to Soviet dissident Vasili Mitrokhin, O’Riordan is approached by IRA leaders Cathal Goulding and Seamus Costello with a view to obtaining guns from the Soviet KGB to defend Irish republican areas of Belfast during the communal violence that marks the outbreak of the Troubles. Mitrokhin alleges that O’Riordan then contacts the Kremlin, but the consignment of arms does not reach Ireland until 1972. The operation is known as Operation Splash. The IRA splits in the meantime between the Provisional IRA and the Official IRA and it is the latter faction who receives the Soviet arms. Mitrokhin’s allegations are repeated in Boris Yeltsin‘s autobiography.
O’Riordan’s book, Connolly Column – The Story of the Irishmen who fought for the Spanish Republic 1936–1939, is published in 1979 and deals with the Irish volunteers of the International Brigade who fought in support of the Spanish Republic against Francisco Franco in the Spanish Civil War (1936–1939). An updated version of the book is reprinted in 2005 and is launched by the Lord Mayor of Dublin, Cllr. Michael Conaghan at a book launch at SIPTU headquarters, Liberty Hall. The book is the inspiration for Irish singer-songwriter Christy Moore‘s famous song “Viva la Quinta Brigada.”
In 1991, O’Riordan’s wife dies at the age of 81 at their home. He continues to live in their family home before moving to Glasnevin in 2000 to be close to his son Manus who lives nearby. He lives there until falling ill in November 2005 and is taken to the Mater Hospital. His health rapidly deteriorates and he quickly develops Alzheimer’s disease. Soon afterwards he is moved to St. Mary’s Hospital in the Phoenix Park where he spends the final few months of his life, before his death at the age of 88 on May 18, 2006.
O’Riordan’s funeral at Glasnevin Crematorium is attended by over a thousand mourners. Following a wake the previous night at Finglas Road, hundreds turn up outside the house of his son Manus and traffic grounds to a halt as family, friends and comrades – many of whom are waving the red flag of the Communist Party of Ireland – escort O’Riordan to Glasnevin Cemetery. A secular ceremony takes place led by Manus O’Riordan, Head of Research at SIPTU, with contributions from O’Riordan’s family, Communist Party general secretary Eugene McCartan and IBMT representative Pauline Frasier.