 He succeeded his probable uncle, Hodo, as Margrave of the Saxon Ostmark including Mark Lausitz (Lusatia) in 993 upon the death of margrave of Lusatia Hodo or Odo I, Margrave of the Saxon Ostmark.Gero was created Count of Hassegau in 992, just a year before becoming margrave.He died in his territory in battle with a Polish army of Boleslaw I in Gau Diadesi and was buried in his family's monastery of Nienburg.