Despite early opposition from his fellow German dukes, Henry the Fowler was eventually able to persuade the dukes of Bavaria and Swabia to support his claim to the crown. More importantly, he won their support for his son, Otto, who later became the first crowned Holy Roman Emperor. An able leader, Henry was successful in driving off invading Magyars, and himself invaded territories to the north, where the Danes had harried the Frisians off to the sea. Widukind of Corvey in his Rex gestae Saxonicae reports that the Danes were subject of Henry the Fowler. Henry incorporated territories held by the Wends, who together with Danes had attacked Germany, into his own kingdom.
Henry's military skills and ambition helped him to increase his kingdom, into which he was able to incorporate the Duchy of Bavaria and the Kingdom of Lotharingia. His sons, Henry (also called the Quarrelsome) and Bruno (later canonized as St Bruno), inherited these (now both) duchies.