This monograph places Na Fianna Éireann within a wider international historiographical context. It shows that the organisation was part of a broader trend of pseudo-military scouting groups created in anticipation of the coming war in Europe with comparable groups formed in Poland and Germany, as well as Britain. The Fianna, an openly republican organisation, however, was created by Countess Markievicz and Bulmer Hobson specifically to combat the imperialistic influence of the Baden-Powell boy scouts and indoctrinate children with Irish republicanism. The group aimed to train boys and some girls (although as Marnie Hay notes the youth group eventually excluded girls from the organisation) to become part of the future army of Ireland and to fight for Irish independence: ‘to pledge themselves to the future Republic of Ireland’.

Members of the Fianna went on to fulfil a variety of roles within the struggle for Irish independence. Younger members generally undertook a support role in carrying dispatches, disseminating propaganda and intelligence work whereas older members participated in raids, but more often than not graduated to the Irish Volunteers, later Irish Republican Army (I.R.A.). In fact, Fianna and I.R.A. members record clashes in operations which ultimately led to the formation of the army agreement of 1921 which, to a degree, brought the Fianna under the control of the I.R.A. and implemented a system whereby Fianna members, upon reaching the age of eighteen, would automatically be transferred to the I.R.A. ensuring a steady flow of new recruits and soldiers. The Fianna, as an organisation, was officially anti-Treaty, although some members did defect from the youth group to join the national forces. Marnie Hay's monograph ends in 1923 with the conclusion of the Irish Civil War, although while the Fianna did continue to function afterwards this is not fully explored.

However, Hay's study aims to ‘provide an accessible account of the organisation's earlier history and contribution to the Irish Revolution’ (p. 3). This monograph is well thought-out, highly readable and well written, and it fulfils the objective Hay sets out: to examine how ‘Na Fianna Éireann became the military trail blazers of the Irish nationalist movement’ (p. 2). Despite the youth group's participation in all the events of the Irish revolutionary period, this is the first piece of academic scholarship to provide a study devoted solely to the Fianna since John R. Watts's unpublished Ph.D. thesis in 1981. Other, more recent, publications include a study of Scouting in Ireland by J. Anthony Gaughan (2006) and a narrative history of the Fianna by Damian Lawlor (2009).

Hay's nuanced monograph significantly builds upon her previous articles dedicated to the youth group. Instead of a linear study charting the group's evolution from its formation in 1909 to the end of the Irish Civil War in 1923, Hay has written distinct thematic chapters dealing with different aspects of the group, such as ‘who joined the Fianna’ and ‘moulding minds and marketing martyrdom’. This approach offers the reader an analysis of several aspects of the Fianna's membership, evolution and, indeed, contribution to the Irish Revolution. The chapter on propaganda depicts the attempts made by the Fianna to indoctrinate and persuade other youths to join the nationalist cause, and its contribution to the dissemination of anti-recruitment posters as well as campaign literature. ‘Who joined the Fianna?’ unpicks the backgrounds of the children of this revolutionary generation who were drawn to the Fianna as well as charting what happened to members after they left, noting the group's influence and impact upon their future careers as activists, politicians or businessmen.

The book also provides a valuable and useful appendix that includes a list of all known Fianna members to date as well as battalions and their strength at different dates. Due to source limitations, some aspects or events that certain members took part in are repeated in different chapters; chapters three and eight could have been moulded into one chapter, for instance. The sources used by Hay however are noteworthy and are carefully scrutinised. The use of the sources, including the Bureau of Military History witness statements, Military Service Pensions Collection, Dictionary of Irish Biography, and newspapers, builds upon our understanding of the youth group. Hay, with her wealth of research, proceeds carefully to unravel its inner workings and over-lapping networks. Overall, this study provides a thoughtful and well-constructed analysis of Na Fianna Éireann which is a must-read for both academics and non-academics alike.