After joining the Prussian Army of Frederick the Great, he returned to England and in 1771 purchased an Ensigncy in the 1st Regiment of Footguards.

He then purchased a captaincy in a German Jäger rifle company bound for North America to campaign in the American Revolutionary War.

As a consequence, the legion's cavalry was badly mauled by Patriot militia that had set up an ambush in the town centre.

He also became involved in a minor literary feud, in 1789, publishing An Address to the Army; In Reply To 'Strictures', by Roderick M'Kenzie (Late Lieutenant in the 71st Regiment) On Tarleton's History of the Campaigns of 1780 and 1781.

[1] They became great friends, the prince apparently admiring Hanger's sense of humor and his exploits, both military and with women, and appointing him Equerry in 1791.

A number of prints show him in the circle of Charles James Fox, a prominent Whig opponent of the Tory prime minister William Pitt the Younger in the last years of the 18th century.

On the death of his brother William, the 3rd Baron, in December 1814, the barony of Coleraine descended to Hanger, but he declined to assume the title.

He was survived by a second wife, Mary Anne (possibly his housekeeper) and a son, John Greenwood Hanger (baptized 1817, died 1847).