On the breaking out of the war with France all officers were required for active service, and Captain Acland exchanged into the 3rd regiment or Buffs on 9 March 1793.
He became colonel in 1803, and, after serving at the Battle of Maida, was appointed brigadier-general, and ordered to take command of a brigade fitting out at Harwich for Portugal in 1808.
His brigade sailed in company with one under Brigadier-General Anstruther in May, and on reaching the Douro found orders from Sir Arthur Wellesley to proceed to Maceira Bay.
As it was, Acland by a flank fire helped Anstruther to drive down the main French attacking column, which was his chief important service.
Ill-health made it necessary for him to leave Portugal soon after the battle, and deprived him of the glory of serving, like Anstruther, under Sir John Moore.