Though he started under a regency, he showed himself to be a forceful leader, continuing Savoy's emergence as a power in Europe politically and militarily.

Since he was only nine years old, his father's will left two cousins as co-regents: Amadeus III of Geneva and Louis II of Vaud.

[6] When the young Angevin queen Joanna I of Naples took the throne, several in northern Italy sought to take advantage of her inexperience and seize her lands there.

John II, Marquess of Montferrat led the first attacks, while James of Piedmont, a cousin and vassal of Amadeus, backed the queen.

This treaty included provisions for Galeazzo II Visconti to marry Bianca of Savoy, sister of the count.

When he and his followers were attacked in August 1351 Pope Clement VI excommunicated the rebels, and Amadeus sent in thirty knights.

On 6 June 1352, the count of Savoy made an alliance with Albert II, Duke of Austria for mutual aid in conflict.

John II of France intervened and settled a truce in July, as he was hoping to use both armies in Gascony against the English, continuing the Hundred Years' War.

Pope Innocent VI and John both sent delegations to negotiate a truce, but Amadeus and Hugh continued their fight until April 1354.

[15] In a treaty concluded in Paris in 1355, Amadeus agreed to exchange territory in Dauphiné beyond the rivers Rhone and Guiers, in exchange for recognition as the undisputed sovereign of Faucigny and the county of Gex, as well as becoming the suzerain lord over the Counts of Genevois, all of whose titles had been the subject of earlier contention between the Counts of Savoy and the Dauphins of Viennois.

Amadeus also forced the Marquess of Saluzzo to pay him tribute, thus extending his rule to the Italian side of the Alps.

The following year Charles IV ceded his rights to the crown of Arles to Louis I of Anjou after, however, transferring the County of Savoy to jurisdiction of the Kingdom of Germany.

Amadeus initiated a minor crusade (with 15 ships and 1,700 men) in 1366 against Murad I of the Ottoman Empire to aid his cousin, John V Palaiologos, the Byzantine Emperor, son of the Dowager Empress, Anne of Savoy.

In this campaign, Amadeus joined forces with Francesco I of Lesbos, and the Hungarian king Louis the Great, and they drove the Turks from Gallipoli.

[17] From 1372 to 1373 he fought alongside Enguerrand VII, Lord of Coucy in Italy as a part of the Papal forces against the Visconti family.

[23] Eventually, it was agreed under the Treaty of Turin that as a compromise the island, after being depopulated and demilitarised, should be formally entrusted to Amadeus, Count of Savoy, a cousin to the Palaiologos imperial family.

[24] Later Amadeus would be persuaded by Antipope Clement VII (Avignon Obedience) to accompany Louis I, Duke of Anjou, on an expedition to Naples.

They had three children: Amadeus is one of the main characters in the New Weird novel La luce di Orione (2007) by Valerio Evangelisti.

He is also a supporting character in the Chivalry series by Christian Cameron, with his epithet providing the title of the third novel, The Green Count (2017).