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city, Thuringia Land (state), east-central Germany. It lies on the Saale River, east of Weimar. First mentioned in the 9th century as Jani, it was chartered in 1230 and belonged to the margraves of Meissen from the mid-14th century. The house of Wettin, which held the margraviate and (after 1423) the electorate of Saxony, was divided in 1485, and Jena fell to the dukes of the Ernestine branch. From 1672 to 1690 it was the centre of the duchy of Saxe-Jena, and it remained a ducal residence until 1918. Napoleon won a notable victory over the Prussian army on the heights north of Jena in 1806 (see Battle of Jena).