Mayor of the Palace
Tassilo, then still a child, began his rule as a Frankish ward under the tutelage of his uncle, the Carolingian Mayor of the Palace Pepin the Short (later king) after Tassilo's father, Duke Odilo of Bavaria, had died in 748 and Pepin's half-brother Grifo had tried to seize the duchy for himself. Pepin removed Grifo and installed the young Tassilo as duke, but under Frankish overlordship.