This is a book of broad canvases: cultural demobilisation in the aftermath of the First World War; international diplomacy; and the extraordinary charisma of one man in what was to become a peace movement of European dimensions. It is also a book in which the talents of the author are equal to the breadth and intricacy of the material. In The disarmament of hatred, Gearóid Barry offers a study of the Catholic deputy and social activist Marc Sangnier that is not a traditional biography, but rather an account of his pacifism that engages with wider questions, not least the contribution of political Catholicism to the reshaping of European civic spaces after the First World War. Barry's concern is to illuminate the religious dimension of transnational pacifism, which he achieves through a sensitive analysis of rhetoric, symbolism, ‘liturgies of peace’ and the construction of important – albeit sometimes transient – connections across national boundaries. With Sangnier as the book's central focus, The disarmament of hatred takes shape through a series of chronological case studies. Early chapters trace Sangnier's evolution from wartime propagandist to post-war pacifist, and from the ‘daring’ social Catholicism of his pre-war Sillon movement to the internationalism of his high-profile peace congresses in the interwar period (Sangnier himself was to organise twelve such congresses, with Franco-German reconciliation a powerful priority). The central chapters then analyse Sangnier's importance in promoting the ‘disarmament of hatred’ – the phrase was his own – through politics, diplomacy and social activism, with a particularly detailed analysis of the liturgical and musical dimensions of Sangnier's peace congress at Bierville in 1926. Finally, the focus shifts to Sangnier's adoption of a more radical antimilitarist position in the 1930s, and thereby also to the well-studied dilemma of combining pacifism and anti-Fascism in the pre-war years. As a study of Sangnier's pacifism, and as a contribution to the transnational history of the period, this is an important book. The range of historiographical and archival research is impressive, as is the ability to relate striking detail to wider questions. Though Sangnier is sympathetically portrayed, Barry is none the less careful to document the reactions of his detractors (for whom he was variously both an ineffectual bourgeois pacifist and a ‘Bolshevik Christian’). And though this is primarily a study of French society and politics, it also moves deftly from national to international contexts and concerns, not least in the cases of youth activism and Christian democracy. If there are areas that might be more fully developed – such as the grass-roots experience of Sangnier's peace congresses – the overall picture is a fascinating one. This is a book that will appeal to those interested in the political, cultural and ecclesiastical history of the interwar period.