The group is said to be the only military group in Ireland never to have yet killed or targeted a civilian. As of 2004, the CIRA is not believed to have an established presence or capability of launching attacks on the island of Great Britain. In 2004 the U.S. government believed the CIRA to consist of fewer than fifty fully active members. The U.S. government suspected the CIRA of receiving funds and arms from supporters in the United States. It is also believed that, in cooperation with the "Real" IRA, the CIRA may have acquired arms and material from the Balkans. The Irish Republican Army first emerged as the army of the Irish Republic that had been declared at the Easter Rising of 1916 and affirmed by the First Dail in January 1919. It was an amalgamation of the Irish Volunteers and the Irish Citizens Army, which were formed before World War I and which had played a part in the Easter Rising. The Irish Defense Forces, the Official and Provisional IRA and the "Continuity" and "Real IRA" all lay claim to the title glaigh na heireann (in the Irish language, Irish Volunteers).

Michael Collins took an active role in reorganizing the IRA. Its formation and its subsequent development were inextricably intertwined and interrelated with the subsequent political history of the Irish Free State (which became the Republic of Ireland in 1937) and Northern Ireland and any consideration of the IRA therefore needs to be set firmly in context.

Michael Collins studied the tactics of the Russian Peoples' Will and the writings of earlier anarchists and terrorists. He used these items as an inspiration for strategy and launched a guerrilla war against the British. After obtaining a list of British and loyalist Irish police and intelligence officers, Collins sent IRA terrorists to their homes and killed them. He attacked police stations and symbols of British authority. A master of terrorist strategy, Collins continued a campaign of terror against unionists and the RJC.

The Government of Ireland Act 1914, more generally known as the Third Home Rule Act, was an Act of Parliament passed by the British House of Commons in May 1914 which sought to give Ireland national self-government within the United Kingdom of Great Britain and Ireland. Though it received the Royal Assent in September 1914, its implementation was postponed until after the First World War, at that stage expected to last only a matter of months....

However the outbreak of the Easter Rising in 1916 and the unexpected electoral success of Sinn Fein in the 1918 general election made any enactment of the Act redundant. It was never implemented but was eventually replaced by the Government of Ireland Act 1920, which was to give Home Rule to six counties in the northeast (Northern Ireland) and to twenty-six counties in the north-west and south (the so-called "Southern Ireland"). "The Easter Rising of 1916 was the defining event in the history of Irish republicanism. Many would regard the Proclamation of the Republic issued then as the founding document of the IRA. It declared an independent Republic and pledged republicans to 'equal rights and equal opportunities' for all the Irish people."
For a minority of nationalists, the home rule conceded was judged to be too little, too late. In the Easter Rising of 1916, these nationalists staged a rebellion against British rule in Dublin and in some other isolated areas. Weapons had been supplied by Germany, under the auspices of a leading human rights campaigner, Sir Roger Casement. However the plot had been discovered and the weapons were lost when the ship carrying them, the Aud, was scuttled rather than allow the arms to fall into British hands.

The rebellion was largely centered on Dublin. The leaders seized the Dublin General Post Office (GPO), raising a green flag bearing the legend "Irish Republic," and proclaiming independence for Ireland, though ironically some republicans in the GPO talked of making Prince Joachim of Prussia the King of Ireland if Germany won the First World War. Although many Irish people believe that the Rising and its leaders had public support, in reality there were calls for the execution of the ringleaders coming from the major Irish nationalist daily newspaper, the "Irish Independent" and local authorities. Dubliners not only cooperated with the British troops sent to quell the uprising, but undermined the Republicans as well. Many people spat and threw stones at them as they were marched towards the transport ships that would take them to the Welsh internment camps.

Public opinion gradually shifted, initially over the summary executions of 16 senior leaders, some of whom, such as James Connolly, were too ill to stand. Opinion shifted even more in favor of the Republicans in 1917-18 with the Conscription Crisis, when Britain tried to impose conscription on Ireland