Cuyler was commissioned as an ensign into the 55th Regiment of Foot in May 1759 during the French and Indian War. He took part in the Battle of Ticonderoga in July 1759 and the Battle of the Thousand Islands in August 1760. He became aide-de-camp to General Sir William Howe in July 1775 and fought at the Battle of Long Island in August 1776, Battle of Brandywine in September 1777 and the Battle of Germantown in October 1777 during the American Revolutionary War before commanding his regiment at the Battle of Monmouth in June 1778.