He was commissioned an ensign in the 2nd Regiment of Foot Guards on 10 April 1715. He was promoted to captain of a company of the 16th Regiment of Foot on 10 June 1717. He briefly transferred to Wynne's Dragoons, and on 21 April 1719, returned to the 2nd Foot Guards as captain of a company and lieutenant-colonel in the Army. In 1725, Howard was appointed Lieutenant-Governor of Carlisle and in 1734 colonel and aide-de-camp to King George II of Great Britain. In 1738, he received the command of the 19th Regiment of Foot, which under him became known as The Green Howards. His regiment took part in the War of the Austrian Succession and in 1742, Howard became brigadier-general. He commanded a brigade in the Battle of Dettingen in 1743 and as result was promoted to major-general a week later. He fought in the Battle of Fontenoy in 1745, and commanded the British Infantry in the Battle of Rocoux in 1746. He was made lieutenant-general in the days after the Battle of Val in 1747.