In March 1923, as the Irish Civil War entered its last stage, an American attorney named John T. Ryan boarded an ocean liner for Germany. Ryan was a leading figure within Clan na Gael, the secret American counterpart to the Irish Republican Brotherhood. He had fought in the 1898 Spanish-American war, arranged German help for the Easter Rising in 1916 and represented the Sinn Féin movement in Germany between 1920 and 1922. On his return to Germany, he carried $100,000 in Clan na Gael funds, together with instructions to arrange a major arms shipment for the anti-Treaty Irregulars in Ireland. If it proved impossible to smuggle the supplies by ship, Ryan hoped to purchase a decommissioned German submarine. Once in Germany, Ryan exhibited the ideological flexibility that was a hallmark of Irish revolutionaries. He worked closely with the German Communist Party, which had aided previous IRA gunrunning schemes. At the same time he approached the right-wing paramilitary groups that had sprung up in the chaotic political atmosphere of post-war Germany, making at least one overture to Adolf Hitler and his National Socialist Party. Though the German government was officially opposed to the export of arms to Irish rebels, there is evidence that Ryan had friends in high places and received assistance from at least one cabinet minister. In addition, he could call on the support of the IRA organisation in Britain, which transmitted correspondence to and from Ireland and provided a channel for the smuggling of small packages of arms.

Ryan's activities illustrates the extent to which the Irish republican movement was an international conspiracy. Given the distribution of the Irish race, this was hardly surprising: by 1911 one-third of all people born in Ireland were living elsewhere. Republican networks in Britain, the United States of America and Europe provided crucial support to the fighters at home, in the form of funds, war material and propaganda. Irish revolutionaries sought assistance from Britain's foreign adversaries, principally Germany and the Soviet Union. The foreign dimension also provided a field for offensive action against British interests, through physical sabotage (terrorism on English soil) and diplomatic sabotage (interference with Britain's relations with other countries).