Hall studied law and was admitted to the bar in New Castle, Delaware, in 1773. Already a member of the Sussex County militia under General Dagworthy, he joined the 1st Delaware Regiment at the beginning of the War of Independence and served as captain under Colonel John Haslet at the battles of Long Island and White Plains. Following Haslet's death at Princeton in January 1777, he became the leader of the regiment, and was promoted to colonel in April 1777. He led the regiment at the Battle of Brandywine and again at the Battle of Germantown where he was wounded on October 4, 1777. The following year he spent recovering, recruiting new soldiers in Wilmington and serving on Courts Martial. He returned to active service in June 1779 at the Middlebrook encampment, spent the inactive summer with the regiment, but returned home in October 1779, complaining of his wound and lack of provisioning. When the Delaware Regiment went to South Carolina in April 1780, Hall did not go. Responding to his continuing requests, the General Assembly authorized some payment, but it was never enough, and finally, in April 1782, Hall resigned his commission.