During the Seven Years' War, Sackville returned to active military service. He had been considered for the post of Commander-in-Chief in North America, which eventually went to Edward Braddock who led his force to disaster during the Braddock Campaign. In 1755, he was promoted to major general and returned to active service to oversee ordnance. In 1758, he was given a fourth regiment and joined the Duke of Marlborough as a lieutenant general. He was sworn of the Privy Council in January 1758.