in 1547, emperor charles v, with the assistance of the duke of alva, captured wittenberg after the battle of mühlberg, where john frederick i was taken prisoner. the duke of alva then presided over a court-martial and condemned john frederick to death. to save his life, the elector conceded the defeat of wittenberg and resigned the government of his country in favor of his relative, maurice of saxony. his sentence was thereupon commuted to imprisonment for life. rescued on 1 september, 1552, he returned to saxony in a triumphal march, and removed the seat of government to weimar.