Appointed lieutenant-general on 27 February 1779, on 29 May he was given command of Plymouth during a possible invasion associated with the Armada of 1779. He seems to have viewed the appointment with some despair and remained in London for a month, attempting to secure a meeting with Lord Amherst, commander-in-chief of the forces. Upon arriving in Plymouth, Lindsay lamented his lack of troops and lack of co-operation from the Board of Ordnance; although Amherst sympathised, he noted troops were thinly stretched across the entire coastline.