In 1596 , it became the capital of one of the new Duchy of Saxe-Coburg under the leadership of Duke Johann Casimirs ( ruled 1596-1633 ) . In 1596 , it was raised to the status of capital of one of the dynasty 's splintered Saxon-Thuringian territories , the new Duchy of Saxe-Coburg under the leadership of Duke Johann Casimirs ( ruled 1596 â `` 1633 ) .