The Germanic Thuringians appeared after about ad 350 and were conquered by the Huns in the second quarter of the 5th century, but by 500 they had established a large kingdom stretching from the Harz mountains to the Danube. As a result of the defeat of their king, Irminfrid, at Burgscheidungen (in the present-day state of Saxony-Anhalt), on the Unstrut River, by the Frankish kings Theodoric I and Chlotar I in 531, their territory was reduced to the Harz mountains and Thuringian Forest region and was governed by Frankish dukes. In the early 8th century the duchy was divided into countships to reassert royal authority, and St. Boniface converted the Thuringians to Christianity. In 908 the Thuringian March (frontier district), set up by Charlemagne against the Slavs, was seized by Otto, duke of Saxony, whose son, Henry I, duke and German king, halted a Magyar invasion of Thuringia at Riade in 933 and strengthened the defenses of the region. After the Saxon royal dynasty died out in 1024, the Ludowing family, through Louis the Bearded, controlled Thuringia. The grandson of Louis was made landgrave of Thuringia by King Lothar II in 1130.
Landgrave Henry Raspe was elected German ‘‘antiking’’ (against Conrad IV) in 1246; he died the next year. After a war over the long-disputed succession (1256–63), Henry III (the Illustrious), margrave of Meissen, of the house of Wettin, made good his claim and invested his son Albert with Thuringia in 1265. Thuringia thereafter remained a possession of the Wettins, and in the 15th century it was divided between Ernestine Saxony, Hesse-Kassel, and several smaller states. Prussia also received sections of Thuringia at the Congress of Vienna (1814–15) and after the Seven Weeks’ War (1866).
In 1920, under the Weimar Republic, several old Thuringian territories (chiefly the Ernestine Saxon duchies) were merged into a new Thuringia, a state of republican Germany, with Weimar as its capital. The frontiers remained anomalous: Erfurt was still attached to the Prussian province of Saxony; there were enclaves belonging to Prussian Saxony or to Prussian Hesse-Nassau surrounded by Thuringian territory; and, conversely, parts of Thuringia were enclaves within Prussian Saxony. After World War II all Thuringia fell to the Soviet-occupied zone of Germany. With the administrative dissolution of Prussia, an enlarged Thuringia state was constituted within East Germany, with rationalized frontiers, including the southwestern part of the former province of Saxony and all the former enclaves; the capital was Erfurt. In 1952, however, when the East German states were dissolved, Thuringia was divided between the Bezirke (districts) of Erfurt, Suhl, Gera, Halle, and Leipzig. Following the reunification of Germany, Thuringia was reconstituted as a state with boundaries similar to those of its post-World War II predecessor from the former East German districts of Suhl, Erfurt, and Gera and from small parts of Leipzig and Halle districts. (See also Saxony.)