The most important source for the situation on the Upper Rhine in Late Classical Antiquity is to be found in the Notitia Dignitatum, a register of all the offices and honours of the Late Roman Empire. The present book deals with one office in the Notitia, the Dux Mogontiacensis, the Commander for the Upper Rhine, residing in Mainz. In it, the author succeeds in re-determining the genesis and purpose of the Notitia. At the same time, this study is the first to meld the regionally-oriented German archaeological research on the Rhine regions in Late Classical Antiquity with studies on the Notitia working in the English-speaking tradition.