On the outbreak of the Spanish Civil War the Irish socialist, Peadar O'Donnell, urged the formation of volunteer regiments to support the Popular Front government. O'Donnell established the Connolly Column, named after his hero, James Connolly.
In December 1936, Frank Ryan and eighty volunteers arrived in Spain. The majority came from the Free State but there were also a group of socialists from Belfast. Those who went included Charlie Donnelly, Eddie O'Flaherty, Paul Burns, Jackie Hunt, Bill Henry, Eamon McGrotty, Bill Beattie, Paddy McLaughlin, Bill Henry, Peter O'Connor, Peter Power, Johnny Power, Liam Tumilson, Jim Straney, Willie O'Hanlon, Ben Murray and Fred McMahon.
After travelling through southern France by train to Perpignan, they went to the training at Albercete in Spain run by André Marty. The Connolly Column suffered heavy losses at Jarama (February 1937). Charlie Donnelly, Eamon McGrotty, Bill Henry, Liam Tumilson and Bill Beattie were all killed during this battle.
Ryan was badly wounded at Jarama in February 1937 and returned to Ireland to recuperate. On his returned to Spain and was appointed adjutant to General José Miaja. Ryan was captured during the Aragón offensive on 1st April, 1938 and was held at the Miranda del Ebro detention camp. He was sentenced to death but after representations from Eamon de Valera his sentence was commuted to thirty years.