Erskine became Colonel-in-Chief of the 26th Foot (Cameronians) in 1782. On 28 September 1787 he was promoted Lieutenant-General. He became a baronet in 1791. After the declaration of war with revolutionary France he served on the staff of the Duke of York in the Flanders Campaign from late 1793. He was present with York at the Siege of Dunkirk from 25 August to 10 September, and commanded the retreat to Furnes after the Battle of Hondschoote. Erskine was given command of the army during York’s absence through the Winter of 1793/1794.