Petersburg, where his father, the 9th Baron Cathcart, was ambassador (1771-1773); studied law in Dresden and Glasgow, and became a lawyer (1776); succeeded to the title on his father's death (1776); purchased a
cornetcy in the 7th Dragoons (June), then transferred to the 16th Light Dragoons in America (June 1777); distinguished himself in the attack on Fort Clinton (October 6, 1777); won promotion to lieutenant (November), and captain in the 17th Light Dragoons (December); served under General Howe in Philadelphia, where he helped to raise the British Legion, later led by Col.