The Decade of Centenaries has witnessed a plethora of new work on the events that led to the establishment of the Irish Free State that has challenged traditional narratives and reinserted those who have been traditionally excluded from established histories. Works focusing on the experiences of women, labor activists, and those outside of Dublin have sought to destabilize the male centric, state-focused narrative of the period in question. However, one area of this research that has not been adequately reinserted into the picture is the role of the Irish abroad, and specifically, the Irish in Britain. The Irish in Britain have been characterized as something of a sideshow to the main event, and the British experiences of some of the key figures in this period are simply a footnote in their main histories. Darragh Gannon's new book seeks to address this.

In Conflict, Diaspora, and Empire: Irish Nationalism in Britain, 1912–1922, Darragh Gannon investigates the development of Irish nationalism in Britain over the course of constitutional crisis, war, and revolution in the early twentieth century. The book has three overarching objectives: it aims to investigate the significance of the Irish in Britain during the Irish Revolution, identify the influences of overlapping contemporary themes, and establish the impact of Edwardian, World War I, and postwar culture on Irish nationalism in Britain. The result is a fascinating study of a complex community who were both molded by British society, and deeply connected by the conflicts and cultures across the Irish Sea.

Gannon follows calls to situate the Irish in Britain in a wider framework. In doing this, he challenges the marginality thesis by arguing that Irish nationalism in Britain was integral to both Irish and British contemporary assessments from the Third Home Bill in the early 1910s to the ratification of the Anglo–Irish Treaty 1922. In doing so, he situates the context of British-based Irish involvement during the War of Independence in a long history of Irish political and cultural nationalism.

The events of this period are not studied in an Irish vacuum, as Gannon explores the wider political landscape during this period and its impact on Irish nationalism in Britain, embedding Irish activism within a broader cultural and political framework of Edwardian Britain. For example, in addition to exploring the struggle for Home Rule and the post-1916 period, Gannon also explores the role of the Irish in Britain during World War I. While some recent works have examined the Irish response to World War I, the responses of the diaspora have been overlooked even though there were over 375,000 Irish-born people living in England and Wales, 174,000 in Scotland, and many more across the British Empire when war broke out in 1914. Gannon situates World War I within the context of the nationalist struggle for Home Rule. Interestingly, he convincingly argues that the cultural atmosphere caused by the war was an essential factor in softening the views of the Irish in Britain toward those who had rebelled against the British during the Easter Rising of 1916, stating that the idea of a solider following orders could be empathized with in the martial atmosphere of wartime Britain, or at the very least, understood. This is an important element for understanding the struggle for Irish self-determination that has often been overlooked in analyses on this period.

Gannon also takes advantage of newly available material to explore these issues. Notably, the files of British-based Irish republicans from the Military Service Pension Collections are utilized to explore the activities and networks of the Irish in Britain during the War of Independence, another burgeoning field in the study of this period that the Irish in Britain have largely been excluded from. As well as using the pension files to explore these gaps, Gannon also utilizes them to explore gender dynamics, arguing that the appeal of the male, Irish Republican was rooted in concepts of Edwardian manliness and physical and moral superiority. There is also an exploration of female nationalists and republicans. This is significant given the marginal status of women in histories of Irish nationalism and republicanism for much of the twentieth century. In conjunction with the Irish in Britain, the role of Irish women in Britain has been long neglected despite the pivotal role they played in dispersing nationalist propaganda, gun running, and sheltering other republicans on the run. Gannon argues that the pension files gave women a rare opportunity to explore their roles and self-perception. Given the lack of work that has been produced on Irish women in Britain during this crucial period, this study would have benefited from an expanded exploration of this; however, the files selected by Gannon give a good insight into the complex emotions of, and activities undertaken by republican women in Britain during this period and demonstrate that their roles were more than auxiliary.

Overall, this is an important contribution to transnational histories of Irish nationalism that convincingly highlights the significance of the Irish in Britain in the establishment of the Irish Free State. Gannon skillfully demonstrates the important role that the Irish in Britain played in shaping policy and attitudes toward nationalism and republicanism, demonstrating that the activities of this community was more than a sideshow to the main events on the island of Ireland by utilizing transnational frameworks and newly available resources. The influence of contemporary British society and political culture is also highlighted, through Gannon's exploration of Edwardian political culture, World War I, and postwar left-wing activism. The role of women in republican and nationalist movements, and gender identities are also effectively explored. It is disappointing that this analysis does not extend into Civil War period, as the status of Irish citizenship in Britain was complicated by the Anglo–Irish Treaty and the unsuccessful deportation of over 100 anti-Treaty individuals in 1923, as it would be interesting to see Gannon's analysis of these developments. However, this does not take away from the important contribution Gannon makes in this work.