As more recruits came in, O'Sullivan organised them as a relatively conventional eighteenth-century army with a staff, cavalry, infantry, artillery, and supporting elements. Command of the field army originally rotated between Lord George Murray and the Duke of Perth, but at Falkirk and Culloden, O'Sullivan was in overall control. The two Scots acted as brigade commanders, with the addition of Perth's brother John Drummond after his arrival in late November.