Thietmar, duke of Saxony

Thietmar (I) (also Thiatmar, Dietmar, or Thiommar) (died 1 June 932), Count and Margrave, was the military tutor (vir disciplinae militaris peritissmus) of Henry the Fowler while he was the heir and then duke of the Duchy of Saxony. He probably kept a small body of elite retainers (though he once feigned at having thirty legions behind him) armed with the latest in military technology and well-supplied with expensive horses. His armored cavalry played a decisive role in winning the Battle of Lenzen on 4 September 929, securing German domination along the Elbe river against West Slavic peoples.

The Duchy of Saxony was originally the area settled by the Saxons in the late Early Middle Ages, when they were subdued by Charlemagne during the Saxon Wars from 772 CE and incorporated into the Carolingian Empire (Francia) by 804. Upon the 843 Treaty of Verdun, Saxony was one of the five German stem duchies of East Francia; Duke Henry the Fowler was elected German king in 919.