On 27 September 1576, Armgard and Walburgis divided their inheritance: Armgard received Rietberg; Walburgis received the Harlingerland.
Sibet Attena, a nephew and aid to Ulrich received the lordships Esens, Stedesdorf and Wittmund, which together formed the Harlingerland.
Edzard's rule was characterized by his energetic approach against his opponents, the East Frisian leaders Hero Oomkens from Harlingerland and Edo Wiemken from Jever, whom he quickly managed to subdue.
Sibet Attena, a nephew and ally of Ulrich, received the lordships Esens, Stedesdorf and Wittmund, which together formed the Harlingerland.