Answer based on context:

Between 1639-53, Scotland was involved in the Wars of the Three Kingdoms, a series of wars starting with the Bishops Wars , the Irish Rebellion of 1641, the English Civil War , the Irish Confederate Wars, and finally the subjugation of Ireland and Scotland by the English Roundhead New Model Army. In Scotland itself, from 1644-45 a Scottish civil war was fought between Scottish Royalists—supporters of Charles I under James Graham, 1st Marquis of Montrose—and the Covenanters, who had controlled Scotland since 1639 and allied with the English Parliament. The Scottish Royalists, aided by Irish troops, had a rapid series of victories in 1644-45, but were eventually defeated by the Covenanters. The Covenanters then found themselves at odds with the English Parliament, so they crowned Charles II at Scone and thus stated their intention to place him on the thrones of England and Ireland as well. This led to the Third English Civil War, when Scotland was invaded and occupied by the Parliamentarian New Model Army under Oliver Cromwell.

Who led the Scottish Royalists?
James Graham