The Irish Citizen Army (ICA) was formed during the Dublin labour dispute in 1913. Its purpose was to enable the locked-out men to defend themselves in clashes with the Dublin Metropolitan Police and to counteract the demoralizing effects of unemployment by providing discipline, cohesion and purpose. The idea of forming a force appears to have been first formally proposed by Captain JR White in 1913 - an ex-army officer from County Antrim, who had been educated at Winchester College and Sandhurst. During a speech in August, James Larkin had already suggested that the workers form a force as Carson had done; he publicly repeated this instruction on 13th November 1913. James Connolly likewise urged the men to train "as they are doing in Ulster". Two weeks later drilling began. According to the ICA constitution, its members were to ‘work for an Irish republic and for the emancipation of labour’. Larkin was anxious that those who enlisted should not only espouse these principles but also be members of unions recognised by the Irish Trade Union Congress.
Despite competition from the Irish Volunteer Force - launched 25th November 1913 - ICA membership quickly reached over 1,000. However, after the dispute was over (January 1914) and the men returned to work, the ‘army’ all but disappeared. But it was Connolly above all who, after his appointment as its commandant and as leader of the Irish Transport and General Workers Union (October 1914), rescued it from terminal decline and welded it into a potent force and potential weapon for his own use. He determined its structure, vetted its officers and imposed a rigid discipline. He also demanded an ideological commitment to revolution and the goal of an independent Irish socialist republic. The force’s guiding principle was that ‘the ownership of Ireland, moral and material, is vested by right in the people of Ireland’. Its membership remained small – 220 in 1916 – but it was otherwise superior to the much larger IVF in its unity of purpose, lack of factional and ideological division and in the quality of its training.
After the outbreak of World War I, Connolly had become increasingly committed to fomenting an insurrection in Ireland. This was reflected in his military preparations with the ICA; he used its headquarters, Liberty Hall as his base. Fearing he might act on his own, and recognising the merits of collaboration, the Irish Republican Brotherhood Military Council informed him of their own clandestine plans for a rising and an agreement was reached. During Easter week, 219 ICA men fought alongside over 1,300 from the IVF. As the appointed leader of both forces in Dublin, Connolly skilfully ensured that the ideological and social divisions and personality clashes, which had hitherto blighted their relationship, were largely overcome. ICA forces were mainly concentrated at the GPO, the College of Surgeons and Dublin’s City Hall. They won volunteer admiration for their professionalism, dedication, and ruthlessness. Two of their leaders were subsequently executed – Connolly and Michael Mallin (ICA Chief of Staff); Countess Markievicz (Mallin`s second-in command) was reprieved. Others were imprisoned or interned. The ICA was not revived after the insurrection. The new leadership of the ITGWU focussed instead on building up the union, safeguarding members’ wages and improving working conditions.