Alexander Leslie pursued a professional British army career and became a prominent field commander in the American Revolution. Joining the army in 1753, he advanced through regimental appointments before serving in North America. In 1776 he led troops in the campaign around New York, including operations on Long Island, at Kip's Bay, Harlem Heights, and White Plains. He also served in the New Jersey campaign that ended with Washington's attack at Princeton.

Leslie took part in the southern campaign and the siege of Charleston in 1780. That autumn Sir Henry Clinton sent him with troops to the Chesapeake to divert American forces and assist Cornwallis's operations. Recalled south, he reached the Carolinas early in 1781 and commanded part of the British army at Guilford Court House. The engagement produced a costly British victory and helped draw Cornwallis toward Virginia.

After the surrender at Yorktown, Leslie commanded the remaining British forces in the southern theater. With offensive operations winding down, he faced problems of supply, raids, and the movement of Loyalists and other people seeking British protection. Under Sir Guy Carleton's orders, he directed the evacuation of Savannah and Charleston in 1782. He returned to Britain, became a major general, and held the colonelcies of the 63rd and later the 9th Regiment of Foot. He died near Edinburgh in December 1794. His final American duties concerned withdrawal and evacuation as much as battlefield command.