The younger brother of King George III, Prince William Henry was created Duke of Gloucester and Edinburgh and Earl of Connaught in 1764. He wanted to pursue an active military career, but neither his physical stamina nor his mental capacity were sufficient to carry a commander’s position on active service. Nevertheless, he became Colonel of several regiments and was made a field marshal in 1793. During the War of Bavarian Succession (1777–1779), he longed to serve under Prince Frederick (later Frederick II) of Prussia, but his request was declined.

In 1766 Gloucester secretly married Maria, widow of James, 2nd Earl Waldegrave, without royal consent. This was concealed for six years until Maria became pregnant. The King banished the couple from court and they spent the next few years in Italy before Gloucester was restored to favour in 1780.