In the period between 1575 and 1625, civic peace in England, Scotland, and Ireland was persistently threatened by various kinds of religiously inspired violence, involving conspiracies, rebellions, and foreign invasions.Religious divisions divided local communities in all three kingdoms, but they also impacted relations between the nations, and in the broader European continent.The challenges posed by actual or potential religious violence gave rise to complex responses, including efforts to impose religious uniformity through preaching campaigns and regulation of national churches; an expanded use of the press as a medium of religious and political propaganda; improved government surveillance; the selective incarceration of English, Scottish, and Irish Catholics; and a variety of diplomatic and military initiatives, undertaken not only by royal governments but also by private individuals.The result was the development of more robust and resilient, although still vulnerable, states in all three kingdoms and, after the dynastic union of Britain in 1603, an effort to create a single state incorporating all of them.R. Malcolm Smuts traces the story of how this happened by moving beyond frameworks of national and institutional history, to understand the ebb and flow of events and processes of religious and political change across frontiers.The study pays close attention to interactions between the political, cultural, intellectual, ecclesiastical, military, and diplomatic dimensions of its subject.A final chapter explores how and why provisional solutions to the problem of violent, religiously inflected conflict collapsed in the reign of Charles I.