John Frederick I, 1503–54, elector (1532–47) and duke (1547–54) of Saxony; last elector of the Ernestine branch of the house of Wettin. Like his father, John the Steadfast, whom he succeeded, John Frederick was a devout Lutheran. A leader of the Schmalkaldic League, he vacillated in loyalty to Holy Roman Emperor Charles V, but he was thrown into opposition when Charles undertook the Schmalkaldic War to crush the independence of the imperial states in Germany and to restore Christian unity. Captured (1547) in the battle of Mühlberg, John Frederick was forced to renounce the electorate in favor of his cousin and enemy, Maurice, duke of Saxony. He retained only a remnant of his lands and the title of duke. He refused to abandon his religious beliefs during subsequent imprisonment (1547–52).
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