Tassilo began his career as a Frankish ward under the tuteledge of Pippen III after his father, Odilo died and Pippin’s half brother Grifo tried to seize the duchy for himself, whereby Pippin removed Grifo and installed the youn Tassilo. Later, (757), the Royal Frankish Annals state that Tassilo became Pippin’s vassal for his lands at an assembly held at Compiegne, where he is reported to have ‘swore numerable oaths’ to Pippin upon ‘relics of the saints’ and ‘promised fealty to King Pippin and his sons Charles and Carloman’. This makes it clear that Tassilo’s office was heldd from the Frankish kingand that he would owe certain dutie, such as military service. However, this highly legalised account is quite out of character for the period which has led some authors, such as K. L. Pearson, to suggest it probably represents a reworking of the origional document by the Royal Frankish Annalist to emphasise Charlemagne’s overlordship over Tassilo during the two rulers period of hostilities. I any case Tassilo clearly felt the pull of independence in 763 when he defaulted on his military obligations to Pippin, leaving the Franks’s Aquitaine campaign on the grounds of ill health. Pearson suggests, this could have been part of an earlier alliance made between Tassilo’s father and the Aquitainian duke during his conflict with Pippin 743. Whatever the motivations behind Tassilo abandoning the campaign the Royal Frankish Annals for that year are particularly scathing of him in their 763 entry claiming he ‘brushed aside his oaths and all his promises and sneaked away on a wicked pretext’. Working on the premise, argued by Pearson, that these annals may have been revised to emphasise Tassilo as a vassal then it seems obvious that this was the beginning of a campaign to show Tassilo as an oath breaker, and, as he was not prepared to carry out a main function of his office, to fight, was unfit for rule. This incident was the lynch pin in Charlemagne and Pope Hadrian’s argument that Tassilo was in no was an independent prince and that he was merely a rebellious vassal deserving of punishment. This punishement was carried out, after much political maovering, in 787 when Tassilo was finally deposed, Interestingly, however, he did not fade into insignificance as the Annals of Lorsch’s entry for 794 see Tassilo brought out once more, at the synod held at Frankfurt, and made to renounce his and his families claims to Bavaria.