Hay was appointed to an important command early in the Seven Years' War, to be part of a force sent to capture Louisbourg, but the commanders vacillated and Hay became discontent. He was overheard making opprobrious remarks about the conduct of the campaign, and was arrested. He spent some time waiting for a ship to be able to return to England, and on arriving there, demanded a court-martial to investigate the facts. The court-martial referred its decision to the king, but Hay died suddenly in 1760, before it could be announced.