He increased the territory of his margraviate by amalgamating the Bohemian and Hungarian frontier marches up to the Thaya, March and Leitha rivers in what is today Lower Austria.

In his time, the colonisation of the remote Waldviertel region was begun by his ministeriales, the Kuenring knights.

Ernest received his epithet due to his fighting against King Béla I of Hungary and his son Géza I on behalf of their rival Solomon according to the chronicler Lambert of Hersfeld.

In the commencing Investiture Controversy, he sided with King Henry IV of Germany and battled against the Saxons, dying at the Battle of Langensalza.

In 1050 Ernest married Adelaide of Eilenburg (1030 – 26 January 1071), daughter of the Wettin margrave Dedi I of Lusatia, who gave him three children: In 1072 he secondly married Swanhild, daughter of Count Sighard VII in the Hungarian March.