By 1710, he was a lieutenant-colonel and missed the December 1710 Battle of Brihuega, when the British rearguard under his cousin James Stanhope was cut off and forced to surrender.

[2] Stanhope was serving as a diplomat in Spain when the War of the Quadruple Alliance began in 1719 and joined the French army under the Duke of Berwick as a volunteer.

Despite policy differences over British involvement in the 1734–1735 war, he kept his position until Walpole's fall in 1742, when he became Lord President of the Council and created Earl of Harrington and Viscount Petersham.

[4] With the support of his political ally the Duke of Newcastle, he was restored as Secretary of State in 1744 but resigned in February 1746 over his preference for an immediate end to the 1740–1748 War of the Austrian Succession.

He was made Lord Lieutenant of Ireland from 1747 to 1751[4] and while his active military career finished in 1720, he received a number of promotions, ending a full General in 1747.