 Ernest Frederick succeeded his father in the Duchy of Saxe-Coburg-Saalfeld when he died in 1764 and established his definitive residence shifted in Coburg.Because of the high indebtedness of the duchy he was compelled by Emperor Joseph II in 1773 to work with a "Debit commission"—an obligatory administration of debts assigned by the emperor—for over thirty years.In Wolfenbüttel on 23 April 1749 Ernest Frederick married with Sophia Antonia of Brunswick-Wolfenbüttel.