From the study of Köchly and Rüstow (1855), the military compendium attributed to Syrianus Magister was conventionally dated to the 6th century A.D. In recent times this supposition has been questioned by some scholars using as their evidence an important series of data and refl ections which date the work to the middle Byzantine period. The purpose of this paper is to review the arguments proposed by previous scholars, in order to examine closely their foundation. Following this, other refl ections concerning dating criteria are discussed, including the debt of Syrianus to previous tactical writings and Byzantine military practice. Finally, useful evidence may come from the beginning of De re strategica, which could include other elements about the political thoughts of the author. Keywords: Syrianus Magister, Byzantine polemography, De re strategica, Iustinianus, Leo the Wise.