The New Scots, the men of the army the Scottish covenanters sent to Ireland, were the most formidable opponents of the Irish confederates for several crucial years in the 1640s, preventing them conquering all Ireland and destroying the Protestant plantation in Ulster. The greatest challenge to the power of the covenanters in Scotland at a time when they seemed invincible came from a largely Irish army, sent to Scotland by the confederates and commanded by the royalist marquis of Montrose. Thus the relations of Scotland and Ireland are clearly of great importance in understanding the complex ‘War of the Three Kingdoms’ and the interactions of the civil wars and revolutions of England, Scotland and Ireland in the mid-seventeenth century. But though historians have studied Anglo-Scottish and Anglo-Irish relations extensively, Scottish-Irish relations have been largely neglected. Scottish Covenanters and Irish Confederates attempts to fill this gap, and in doing so provides the first comprehensive study of the Scottish Army in Ireland.