Amherst served in the War of the Austrian Succession becoming an aide to General John Ligonier and participating in the Battle of Dettingen in June 1743 and the Battle of Fontenoy in May 1745. Promoted to lieutenant colonel on 25 December 1745, he also saw action at the Battle of Rocoux in October 1746. He then became an aide to the Duke of Cumberland, the commander of the British forces, and saw further action at the Battle of Lauffeld in July 1747.