The executions during the Irish Civil War took place during the guerrilla phase of the Irish Civil War (June 1922 – May 1923). This phase of the war was bitter, and both sides, the government forces of the Irish Free State and the anti-Treaty Irish Republican Army (IRA) insurgents, used executions and terror in what developed into a cycle of atrocities. From November 1922, the Free State government embarked on a policy of executing Republican prisoners in order to bring the war to an end. Many of those killed had previously been allies, and in some cases close friends (during the Irish War of Independence 1919–1921), of those who ordered their deaths in the civil war. In addition, government troops summarily executed prisoners in the field on several occasions. The executions of prisoners left a lasting legacy of bitterness in Irish politics.
The use of execution by the Irish Free State in the Civil War was relatively harsh compared to the recent British record. In contrast with 77 official executions by the Irish Free State government, the British executed only 24 IRA volunteers during the 1919–21 conflict.
Michael Collins, commander of the Free State's National Army, had hoped for a speedy reconciliation of the warring Irish nationalist factions, demanding that Republicans must accept the people's verdict and then could go home without their arms... We want to avoid any possible unnecessary destruction and loss of life. We do not want to mitigate their weakness by resolute action beyond what is required
However, following the death of Collins in an ambush on 22 August 1922, the Free State government, under the new leadership of W. T. Cosgrave, Richard Mulcahy and Kevin O'Higgins, took the position that the Anti-Treaty IRA were conducting an unlawful rebellion against the legitimate Irish government and should be treated as criminals rather than as combatants. O'Higgins in particular voiced the opinion that the use of martial law was the only way to bring the war to an end.