Otto, the oldest son of Henry I…

Otto, the oldest son of Henry I and Matilda, first gains experience as a military commander when the German kingdom fights against Slavic tribes on its eastern border.

While campaigning against the Slavs in 929, Otto's illegitimate son William, the future Archbishop of Mainz, is born to a Slavic mother.

With Henry's dominion over the entire kingdom secured by 929, his family is given the right of sole succession over the kingdom.

Henry has the arrangement for his succession ratified by an Imperial Diet at Erfurt.

After his death, his lands and wealth are to be divided between his four sons: Thankmar, Otto, Henry, and Bruno.

Departing from customary Carolingian inheritance, the King designates Otto as the sole heir apparent without a prior formal election by the various dukes.