The region remained part of Savoy lands, with the exception of a French occupation, 1539–1563. The title Duke of Aosta was given to various princes of the dynasty of Sardinia, second sons of the reigning monarch. It can be compared to the English Duke of York, French Duke of Orléans, Swedish Duke of Södermanland and the Scottish Duke of Albany.
Prince Aimone succeeded to the title Duke of Aosta on 3 March 1942, following the death of his elder brother Prince Amedeo, 3rd Duke of Aosta, in a British Prisoner of War camp in Kenya. In the Autumn of 1942, Aimone contacted Allied forces via his courier, the consul general Alessandro Marieni, about the possibility of a peace settlement between Italy and allied forces.