[3] In 1550, under Georg II von Gleichen [de] work began on Schloss Ehrenstein at the site of the former 8th century monastery.

In 1869, the Hohenlohe family sold the Grafschaft Gleichen including the castle and town of Ohrdruf to the Duchy of Saxe-Gotha.

[4] The nearby Truppenübungsplatz Ohrdruf [de] (military training area) served as a POW camp during World War I, housing around 20,000 prisoners.

[8][9] According to German historian Rainer Karlsch, the facility built at nearby Jonastal was one of two locations where Kurt Diebner's team tested its nuclear energy project.

[citation needed] Ohrdruf is believed to be the place where the historical Compiègne Wagon was blown up in an air attack in 1944.

[7] The military training area of Truppenübungsplatz Ohrdruf was taken over in July 1945 by the Red Army, since Thuringia became part of the Soviet occupation zone.