The Duchy of Thuringia was an eastern frontier march of the Merovingian kingdom of Austrasia,[1] established about 631 by King Dagobert I after his troops had been defeated by the forces of the Slavic confederation of Samo at the Battle of Wogastisburg.

The former kingdom of the Thuringii arose during the Migration Period after the decline of the Hunnic Empire in Central Europe in the mid 5th century, culminating in their defeat in the 454 Battle of Nedao.

His son and successor Hermanafrid married Amalaberga, a niece of the Ostrogoth king Theoderic the Great, thereby hedging the threat of incursions by the Merovingian Franks in the west.

The Thuringian realm was shattered: the territory north of the Harz mountain range was settled by Saxon tribes, while the Franks moved into the southern parts on the Main River.

His successors of the local ducal dynasty, the Hedenen, supported missionary activity within the duchy, but seem to have lost their hold on Thuringia after the rise of the Pippinids in the early eighth century.

In 1111/12 Count Herman I of Winzenburg is documented as a Thuringian landgrave, the first mention of a secession from Saxony, however, he later had to yield as he sided with the Papacy during the Investiture Controversy.

In the "Golden Age" under Hohenstaufen rule, Thuringia became a centre of Middle High German culture, epitomized by the legendary Sängerkrieg at the Wartburg, or the ministry of Saint Elizabeth, the daughter of King Andrew II of Hungary.

When Landgrave Louis IV married her in 1221, the Ludowingian dynasty had accomplished the advancement to one of the mightiest princely houses of the Holy Roman Empire.

The landgraves maintained close ties with the Teutonic Knights, the order established several commandries east of the Saale, as in Altenburg and Schleiz, with the administrative seat of the Thuringian bailiwick in Zwätzen near Jena.

However, when Frederick was declared deposed by Pope Innocent IV in 1246, he secured the support by the archbishops Siegfried III of Mainz and Conrad of Cologne and had himself elected German anti-king.

Mocked as rex clericorum his rule remained disputed, though he was able to defeat the troops of Frederick's son Conrad IV he died one year later.

His heritage was claimed by both the Wettin margrave Henry III of Meissen, son of Judith of Thuringia, and Duchess Sophie of Brabant, daughter of late Landgrave Louis IV - a conflict that led to the War of the Thuringian Succession.