After the Diet of Speyer in 1526 he tried to approach Brandenburg. Due to Brandenburg claims and the refusal of the Pomeranian estates to cooperate, the negotiations took until 1529. In the meantime, Brandenburg once again threatened to resolve the conflict using its military. But on 26 August 1529, a compromise was struck, the Treaty of Grimnitz, with Elector Joachim I of Brandenburg thanks to the mediation of the Dukes Eric I of Brunswick-Göttingen-Calenberg and Henry the Younger of Brunswick-Wolfenbüttel. George would marry Joachim's daughter Margaret of Brandenburg and Brandenburg would recognise Pomerania's imperial immediacy.
