At the death of Valdemar IV in the spring of 1312, he immediately succeeded his father as Duke of Schleswig. Shortly afterwards, he participated in the expedition of his feudal overlord, King
Eric VI of Denmark, to
Rostock. During this expedition, on 30 June in the camp outside
Warnemünde, he was formally installed as Duke. As Duke, he claimed the
fief of
Langeland after his deceased uncle,
Eric Longbone, Lord of Langeland. These and other disputes with King Eric, were settled at the settlement in
Horsens on 9 August 1313, in which Eric renounced his claims to Langeland but received the
Crown lands of the
Duchy of Schleswig. When King
Eric VI of Denmark died in 1319, Duke Eric was briefly candidate to the vacant throne of Denmark. Ultimately, Eric VI's brother,
Christopher, was elected King. However, part of the price Christopher had to pay to accede to the throne, was to accept the right of Duke Eric to the fief of Langeland. ==Death==