His brothers Pietro and Aimone spurred a revolt in Aosta Valley against Amadeus, but he was able to crush it with the help of Manfred III of Saluzzo and Boniface II of Montferrat, who were his sons-in-law.

As the eldest son of Thomas I of Savoy, Amadeus inherited the county and associated lands on his father's death in 1233.

[2] These territories were on the frontiers of Savoy lands, designed to encourage the brothers to expand the county rather than diminish it.

[7] In July 1243, Amadeus and his brother Thomas were ordered by Enzo of Sardinia to join him in a siege of Vercelli, which had recently switched allegiances from the Empire to the Pope.

He also signed a treaty with Henry III on 16 January 1246 which gave rights of passage through the passes to the English in exchange for an annual payment of 200 marks.

He had gathered his army in Turin, and ordered those still loyal to him in the kingdoms of Arles and France to meet at Chambéry (the capital of Savoy).

On 8 November 1248, Frederick asked Amadeus and his brother Thomas to go to Lyon and start negotiations for peace.