[2] Franz completed his elementary and secondary schooling in Greiz, and at the age of twelve he followed in the footsteps of his elder brothers by joining the Wandervogel.

Franz's subsequent career was substantially augmented by the influence of his brother-in-law, the legal historian and SS-Sturmbannführer Karl August Eckhardt [de], who, from 1934 onward, was a principal advisor to the Reich Ministry of Science, Education and Culture (German: Reichswissenschaftsministeriums).

Prior to this appointment, Franz had published extensively on the Peasants' War, indeed, the definitive work on the subject, but had otherwise written very little on wider medieval history.

[6] At Heidelberg, his academic interests took a turn towards population history, which eventually led him to undertake a study of the Thirty Years War.

[9] Jena was also where Franz first made the acquaintance of fellow historian Erich Maschke, with whom he would form a lifelong friendship, and together they began to publish the series "Arbeiten zur Landes- und Volksforschung.

"[10] At the height of the Nazi-era, from 1941 to 1945, Franz taught at the Reichsuniversität Straßburg, specializing in "the history of the Reformation and the Thirty Years' War" and in particular "the study of the German national body.

On 11 November 1933, Franz was one of the signatories of the Vow of allegiance of the Professors of the German Universities and High-Schools to Adolf Hitler and the National Socialistic State.

[11] In it, he declared a fervent hope that they "cleanse themselves of all the dross that still clings to them, in order to be able to devote themselves fully to the new tasks that are set for them today.

[4] After his promotion to Untersturmführer in 1941, Franz was transferred to the Main Office and given supervisory role dealing directly with the Sicherheitsdienst, the Nazi secret police.

He also propagated the ahistorical and antisemitic idea of a Jewish conspiracy to destabilize the Roman Catholic Church, which then triggered the Reformation and the Thirty Years' War.

The elder, Eckhart G. Franz [de] (1931–2015), continued in the family tradition and trained as a historian and an archivist, and served as the head of the Hessian State Archives Darmstadt from 1971 to 1996.

[22] Franz's account Der Deutsche Bauernkrieg (The German Peasant War), published in 1933, was still considered the standard work of research on that subject in West Germany forty years later.