A brutal Civil War erupted across Ireland in June 1922. The IRA, in opposition to the development of a pro-Treaty government, returned to the familiar guerrilla tactics of the War of Independence. Hundreds of dugouts constructed in rural settings were key to the IRA campaign. These secret places offered safe shelter to men on the run, while also allowing for supplies and arms to be stored and prisoners held. Tormore Cave, high in the mountains of County Sligo, in the northwest of Ireland, was one such dugout. Over 30 Republican men sought refuge there for six weeks in September and October 1922. Like most dugouts, Tormore Cave was never mentioned in historical accounts or documentary sources, but its significance was remembered locally. Archaeological excavations conducted on the centenary of its occupation revealed the extensive modifications that had transformed this natural limestone cave into a habitable military dugout, a crucial refuge for combatants whose comrades had been executed or arrested by Government forces. The historical artefacts and environmental material recovered during the excavations, combined with detailed archaeological surveys and analyses, provide a fascinating insight into the conditions endured by those billeted there. The lives of the men and women directly associated with the cave dugout are explored, including an in-depth study of IRA General Officer Commanding Billy Pilkington - a key figure during the Irish revolutionary period who has, until now, been largely overlooked. An Irish Civil War Dugout: Tormore Cave, County Sligo adopts a multidisciplinary approach, the first of its kind in an Irish context, combining archaeology, local and military histories, family memories, community recollections, and landscape studies. This groundbreaking study - the first archaeological excavation of a Civil War site in Ireland, facilitates a wider discussion of the role of dugouts in guerrilla warfare. By focussing in detail on one site at a local level, this book provides a unique and valuable contribution to the Irish revolutionary period on a regional and national scale.