He also intervened in Germany, where he forced the duke of Bavaria, Tassilo, to become his vassal.
In 763, however, Tassilo abandoned Pippin during an expedition against Aquitaine.
On the other hand, we know that the law is anterior to the reign of Duke Tassilo III.
Tassilo III., duke of the Bavarians, who had on several occasions adopted a line of conduct inconsistent with his allegiance to Charles, was deposed in 788 and his duchy placed under the rule of Gerold, a brotherin-law of Charles, to be governed on the Frankish system (see Bavaria).
Tassilo, a member of this family, is said to have built a castle at Zollern early in the 9th century; but the first historical mention of the name is in the Chronicon of a certain Berthold (d.
In 785 he was made bishop of Salzburg and, in 787 was employed by Tassilo III., duke of the Bavarians, as an envoy to Charlemagne at Rome.
Tassilo III., who became duke of the Bavarians in 749, recognized the supremacy of the Frankish king Pippin the Short in 757, but soon afterwards refused to furnish a contribution to the war in Aquitaine.
Moreover, during the early years of the reign of Charlemagne, Tassilo gave decisions in ecclesiastical and civil causes in his own name, refused to appear in the assemblies of the Franks, and in general acted as an independent ruler.
Tassilo appears to have done homage in 781, and again in 787, probably owing to the presence of Frankish armies.
It was almost entirely destroyed in the war of Charlemagne against Tassilo III., duke of Bavaria; and after the dissolution and division of that empire, it fell into the hands of the dukes of Swabia.