William Thompson was born in Ireland, Great Britain on 5 July 1736, later immigrating to Carlisle, Pennsylvania in the Thirteen Colonies. Thompson enlisted in the British Army during the French and Indian War in 1754, and fought in the Kittanning Expedition under John Armstrong, and in 1775, after serving in the British military for decades, became a Brigadier-General in the Continental Army. Thompson fought at the Battle of Bunker Hill at the start of the American Revolutionary War, and he later took part in the invasion of Canada. In June 1776, he was defeated at the Battle of Trois-Rivieres and captured after being defeated by the British. Thompson was exchanged for Baron Riedesel in 1781 and returned to Carlisle, Pennsylvania after his release, dying there on 3 September 1781.