This decision was echoed in Ireland by various left-wing groups; the chief organizers of this effort were Sean Murray, Peadar O'Donnell, and Frank Ryan.
he was in contact with Bill Scott, a volunteer with the Thälmann Battalion who sent regular reports of conditions in Spain, and which Murray published in the party newspaper, The Worker.
On his return to Ireland, O'Donnell urged the formation of Irish volunteer regiments to support the Popular Front government.
Already a small group, some left-leaning IRA or ex-IRA men had formed the breakaway Republican Congress in 1934, which also divided later that year.
Bill Gannon, former IRA member who had been among the assassins of Justice Minister Kevin O'Higgins in 1927, and who later joined the Irish Communist Party, had a major role in the recruitment and organising.
The unit first saw action on the Andalusian front near Cordova as part of the 12th (French) IB battalion where they helped repulse a Nationalist attack.
Ryan wrote of the importance of workers solidarity outweighing national sentiment,[14] though he also on one occasion threatened to shoot an English volunteer when he found out that he had served in the Black and Tans in the Irish War of Independence.
As a result of these tensions, some of the Irish left the British to join the 17th (American) Lincoln Battalion, another part of the XV Brigade.
In July the XV Brigade took part in the battle of Brunete, where the Saktvala battalion suffered 450 casualties; the Connolly's, fighting around Villanueva de Canada, lost 7 men killed and many others wounded.
[21] The surviving Irish volunteers were repatriated to Ireland after September 1938, when the Republican government disbanded the International Brigades in the vain hope of securing military aid from other democracies and of getting the fascist troops from Italy and Germany to withdraw.
[24] Christy Moore's song "Viva la Quince Brigada" is about the Irish volunteers who fought with the International Brigades in the Spanish Civil War, and was inspired by Michael O'Riordan's book, Connolly Column.