Duchy of Saxe-Altenburg
However, already in 1485 Elector Ernest of Saxony agreed on the Leipzig partition with his younger brother Duke Albert III. Ernest retained the southern Thuringian estates with Saalfeld; his grandson John Frederick I lost the electoral dignity in the 1547 Capitulation of Wittenberg ending the Schmalkaldic War, along with all his possessions outside of Thuringia. Confirmed by Emperor Maximilian II at the 1570 Diet of Speyer, John Frederick's Ernestine descendants only retained the duchies of Saxe-Weimar and (from 1572) Saxe-Coburg-Eisenach. Upon the death of Duke Frederick William I of Saxe-Weimar in 1602, Saalfeld passed to the newly established Duchy of Saxe-Altenburg, from 1673 Saxe-Gotha-Altenburg.