The result was an invasion of his states twice: in 1174 Susa was set on fire, and in 1187 Henry VI banished him from the Holy Roman Empire and wrested away most of his domains.
This he fostered in parallel with, and notwithstanding, his role as military leader and politician, undertaken reluctantly and only to safeguard his family’s dynastic claims.
With his father he had inherited from his grandfather, Humbert II, the dream of reuniting the fragmented Kingdom of Burgundy, in sharp contrast with a centralising policy of the French royal family.
In those efforts, Humbert was supported by Frederick I Barbarossa, but found himself required to quell neighbouring feudal lords settled among his domains.
Under his guidance the young Humbert made great progress in studies and spiritual formation, foregoing worldly glamour and giving himself to prayer, meditation and penance.
He went there through the offices of Pope Callixtus II, and in 1146 he participated in the Second Crusade, and died on the island of Cyprus in Nicosia on 1 April 1148, where he was buried, leaving the twelve-year-old Humbert as heir.
Humbert's reign lasted forty years, and was characterized by struggles with the Holy Roman emperor, various lords and count-bishops.
The main reason for conflict consisted in the patronage of the bishop of Turin by Frederick Barbarossa, who dreamed of undisturbed dominance of the capital of Piedmont.
This led to a gradual reduction of the possessions and authority of Humbert III on the Italian side, leaving him with the rump territories of the valleys of Susa and Aosta.
He also promoted the foundation of Precettoria of St. Anthony of Ranverso at Buttigliera Alta, not far from the town of Avigliana, entrusting it to Antoniani from Vienne, France.
The death of Humbert III, 4 March 1189 in Chambéry, Savoy at the age of fifty-two, was mourned sincerely by all the people.
The spirituality of Humbert undoubtedly blossomed in an environment of ancient Christian traditions, favoured especially by the example of his father, a pilgrim and crusader in the Holy Land, and of his tutor, Amadeus, Bishop of Lausanne.