Analysing the make-up and workings of the Royalist party in Scotland and Ireland during the civil wars of the mid-seventeenth century, Royalists at War is the first major study to explore who Royalists were in these two countries and why they gave their support to the Stuart kings. It compares and contrasts the actions, motivations and situations of key Scottish and Irish Royalists, paying particular attention to concepts such as honour, allegiance and loyalty, as well as practical considerations such as military capability, levels of debt, religious tensions, and political geography. It also shows how and why allegiances changed over time and how this impacted on the royal war effort. Alongside this is an investigation into why the Royalist cause failed in Scotland and Ireland and the implications this had for crown strategy within a wider British context. It also examines the extent to which Royalism in Scotland and Ireland differed from their English counterpart, which in turn allows an assessment to be made as to what constituted core elements of British and Irish Royalism.