Although Northern Ireland was the first part of the UK to host American troops during the Second World War, historiography of wartime UK has overlooked the significance of the region. The same is true of the historiography of wartime Ireland. Consequently, many studies of Northern Ireland in the 1940s lie in a chasm between those of the UK and Ireland, detached from works with which they should be entwined. Simon Topping seeks to bridge this divide by examining the American military presence in wartime Northern Ireland. Drawing upon previous and new research, Topping comprehensively explores the experiences of American troops in Northern Ireland and evaluates how various elements of society in Northern Ireland, the UK, and Ireland responded to the American presence. Topping argues that the American presence was a catalyst for change insofar as it cemented pre-existing political and religious divisions within Northern Ireland. Those divisions, along with the extent of socially conservative standards, made Northern Ireland a comparatively distinctive region of the UK. The volume demonstrates that these divisions were at the forefront of how the region experienced the war, evidenced in reactions to the Americans. For instance, their arrival met with a fractured response from Unionists and Nationalists, all factions exploited their presence in propaganda, and, despite their shared social conservatism, the Catholic and Protestant churches did not unite to combat the perceived threat to moral standards posed by the more forward-thinking Americans. Topping identifies a discrepancy between rhetoric and reality in Northern Ireland: the sentiments expressed by societal leaders did not always reflect the behaviour of most citizens or, indeed, that of the leaders themselves. The Americans, however, had different concerns. Conditioned by their own society, they focused on questions of race and troops’ welfare, remaining distant from the Irish political question.