Blacker's Boys tells the First World War history of the 9th (Service) Battalion, Princess Victoria's (Royal Irish Fusiliers) (County Armagh), one of thirteen infantry battalions raised in Ireland for 36th (Ulster) Division. It begins with the political context of the long-running Home Rule crisis and the formation of the Ulster Volunteer Force in 1912. It describes the raising of the Battalion in September 1914 from the men of the Ulster Volunteers of Counties Armagh, Cavan and Monaghan, their training, their move to France and early experiences in the trenches. There are detailed accounts of the actions of the Battalion in the Battles of the Somme, Third Ypres and Cambrai, during the German offensive in 1918 and in the Advance to Victory. The main text is supported by detailed appendices that commemorate those who served and include a Roll of Honour of those who died; the awards and decorations earned; biographical summaries of more than 250 officers and details of over 3,400 men who served in its ranks, and an examination of its excellent discipline record. They explain how this Battalion transitioned from comprising only Protestant volunteers from Ulster to one that was a mix of Protestant and Roman Catholic Irishmen, Englishmen from Yorkshire, Nottinghamshire and London, regular soldiers, war-time volunteers and conscripts. The text is supported by full colour maps and many unique photographs.