[citation needed] Born in Würzburg, the son of a factory owner, Gembruch passed his Abitur at the Heinrich-von-Gagern-Gymnasium in Frankfurt am Main in 1937.
After the end of his assistant position he changed for financial reasons to the Military History Research Office in Freiburg im Breisgau.
However, he continued to publish scientific articles, especially in the journal Europäische Sicherheit & Technik [de].
Gembruch habilitated in Frankfurt in 1960 with a thesis on Heinrich Friedrich Karl vom und zum Stein.
In view of his outstanding habilitation, the Faculty of Philosophy in Frankfurt offered him a postdoctoral lectureship.