Most of the time, it was governed in union with the Mark Landsberg; but during the years of 1319-84, it was split off under Balthasar I.
For the next few years, it fell back to his nephew Friedrich VII; but with his death in 1392, the division / co-government of Mark Landsberg / Osterland between his four sons happened, which inevitably led to increasing chaos since further divisions in 1437/42/44, when the most abled heirs died off. This was no help in the Twenty-Year War, where the Wettin states of Thuringia, Meissen and Osterland only acquired the clerical lands of Meissen and Merseburg, which was why they made war against Brandenburg, too.
1529, Dietrich XII (who already was duke of Prussia) introduced primogeniture for his lands, to prevent a further breakup, since his brother and co-regent Balthasar VI also had four sons. In 1643, however, the line of said Balthasar would come to power in Osterland. And in 1750, Balthasar IX inherited Thuringia, after this Wettin sideline died out (which earned him the nickname "lucky bastard"). Now, all the Wettin lands were united again, albeit for a short time.
|List of Roman kings of the HRE|
|Nations that joined the HRE later: Poland | Prussia|
|Nations that left the HRE: Bohemia | Florence | Switzerland|
|Nations that became defunct|