In 1737 De La Warr was appointed Governor of New York and New Jersey. However, he never traveled to America. He continued his military career while being active in the House of Lords and fought at the Battle of Dettingen in 1743 during the War of the Austrian Succession. On 30 August 1737, he was commissioned colonel of the 1st Troop of Horse Guards, an appointment he held until his death. He became a Brigadier-General in 1743, a Major-General in 1745, a Lieutenant-General in 1747 and a General of the Horse in 1765. In 1752 he was appointed Governor of Guernsey, a post he held until his death. In 1761 George III created him Viscount Cantalupe and Earl De La Warr.