Gallienus and his battle cavalry

The emperor Gallienus ruled the Roman empire for fifteen years, from AD 253 until his murder in AD 268, and yet he is hardly known outside academic circles. To put his achievement into context, both Claudius and Nero each ruled for thirteen-and-a-half years, Commodus only twelve.

Admittedly, Septimius Severus reigned for eighteen years, Trajan managed eighteen-and-a-half, Hadrian almost twenty-one, and Antoninus Pius nearly twenty-three.

But the emperors of the third century were generally more ephemeral. Elagabalus reigned for four years; Gordian III, five-and-a-half; Philip the Arab, four-and-a-half; Decius, barely two. In this company, fifteen years is an impressive tally. And yet, for a long time, Gallienus was belittled by scholars.

A good or a bad emperor?

From Edward Gibbon’s Decline and Fall (1776) until Theodor Mommsen’s Die Provinzen von Caesar bis Diocletian (1885), Gallienus was berated as “chaotic and dissolute”. But then, quite abruptly at the outset of the twentieth century, he was suddenly hailed as a brilliant military reformer who had created a rapid action unit of “battle cavalry” to defend the hard-pressed frontiers. So, was this new characterization of Gallienus justified?

Careful sifting of the ancient Greek sources by Léon Homo in a 1903 essay had certainly rehabilitated the emperor’s besmirched reputation to a large degree, but for Alfred von Domaszewski, author of the influential Rangordnung der römischen Heeres in 1908, Gallienus became “that most wondrous of emperors”.

From that time onwards, scholars were convinced that Gallienus was a military genius who had overhauled the Roman army system. This was the gist of the 1976 dissertation by Lukas de Blois, which remained for a long time everyone’s go-to book about Gallienus. Even into the new millennium, we still read about Gallienus’ sweeping military reforms. One writer has been so bold as to subtitle his book “the apogee of Roman cavalry” in a reference to the emperor’s newly created “battle cavalry”.

How had this happened? And — more importantly — was it true? These are the questions that I address in my forthcoming book Phantom Horsemen.