Justinian’s Flea: Plague, Empire and the Birth of Europe

By William Rosen

Jonathan Cape £20, 367 pages

FT bookshop price: £16

Born into a peasant family in 482, Justinian was, in the words of John Julius Norwich, the ”greatest of all the Byzantine Emperors... after Constantine himself”. Reigning from 527 to 565, Justinian recaptured Rome and the western Empire from the Goths (who had toppled the last Roman emperor in 476), recodified Roman law and reconciled it with Christian doctrine and played a leading part in the theological disputes of the day - convening church councils and rebuilding the Hagia Sophia in Constantinople.

Justinian was, as William Rosen engagingly sets out, a master statesman. But his place in history benefited from two pieces of luck. First, he had capable officials. Belisarius, one of history’s most celebrated generals, routinely pulled off spectacular victories. The em-per-or had the further luxury that when he fell out with Belisarius, his septuagenarian substitute, Narses the eunuch, displayed similar brilliance in a campaign against Tortila the Goth.

Justinian’s second piece of luck was his main chronicler, Procopius of Caeseria. Procopius was legal secretary to Belisarius, and so had a close view of all the state’s military and political machinations and manoeuvrings. These he recorded in his History of the Wars. But he also left the secret Anekdota, not discovered until the 17th century. This contained scabrous gossip, much of it about Justinian’s empress Theodora, a former courtesan of (on Procopius’s account) baroque inventiveness.

His luck ran out in 542, when the Black Death erupted in Constantinople. Possibly a quarter of the population of the empire were killed; Justinian himself caught the plague, but survived. At this point, Rosen switches abruptly from the imperial to the microscopic scale, analysing the interactions of bacillus, rat and flea that led to and fuelled the outbreak.

For Rosen, Justinian’s codification of the law was one of the founding pillars of European civilisation. But, paradoxically, the other was his failure, when he was stalled by the plague, to consolidate his rule. Viewed thus, the plague led directly to the rise of Europe. It weakened the imperial state, making space for tiny nations to rise, notably the Franks, but also the Saxons, Lombards and Slavs, which would ”coalesce and combine into polities called France, Spain and England”. The sixth-century ”waves of plagues... sabotaged Justinian’s reconquest, and permitted the European states to survive their infancies”.

By making labour scarce and therefore expensive, the plague acted as a spur to the technological innovations in agriculture that eventually lifted Europe out of poverty. And the rise of Islam, occupying the vacuum left by the retreat of the empire, provided an external enemy against which Europe could define itself. Emperor and bacillus played equally important roles, and Rosen carefully weighs the contribution of each.