This book explores Irish-Scottish connections during the period 1603-1660 and brings important new perspectives to understanding of the Early Stuart 'British' state. It was chiefly in Ireland that the English and Scots intermingled after 1603. The book provides an account of Scottish involvement in the country, which was both more and less pervasive than has been generally understood. Increased Irish-Scottish contact was one of the main consequences of the Ulster Plantation, but this has been under-emphasised in previous studies; likewise the Irish religious and political role in western Scotland and the Isles has been mostly underappreciated. The book explores these themes, and also the importance of the Gaelic world on both sides of the north channel, which played a key role in the transmission of Protestant and Catholic radicalism in Ireland and Scotland. The book identifies some of the limits of England's Anglicizing influence in the northern and western 'British' Isles and the often slight basis on which the Stuart pursuit of a new 'British' state and a new 'British' consciousness operated.