Munro fought in the Irish Confederate Wars under his uncle Robert Monro who commanded the Scottish Covenanter army. Between 1642 and 1646 George and his uncle Robert were generally successful against their enemies the O'Neils, and during that time the Munros put down a rebellion in Ulster in 1642 and captured Belfast in 1644. In 1644 Robert Monro was recalled to Scotland to oppose the Royalist victories of James Graham, 1st Marquess of Montrose, and command of the Scottish Covenanter army in Ireland fell to his nephew George Munro, 1st of Newmore whose principles inclined him to favour the Royalists.
