マイセン辺境伯
In 951, he was first recorded when he succeeded his father as margrave in the "Gau" Serimunt. Between 951 and 978, he was also count in the Saxon Schwabengau. After the death of his uncle Gero the Great in 965, Thietmar inherited large parts of whose vast "Marca Geronis" and upon the death of Margrave Wigbert (before 976) received the Margraviate of Meissen from the hands of Emperor Otto II.