Sabbatius Iustinianus, our Justinian I or Justinian the Great, St Justinian the Emperor of the Orthodox Church, was born a peasant’s child in what is now Macedonia, yet came easily to the throne, having long served as assistant, understudy, co‐emperor, and increasingly the effective ruler for his uncle Justin I (518–527). When he was formally enthroned in 527, seventy‐seven years had passed since the end of the reign of Theodosios II, and its strategic innovations had been absorbed, consolidated, and institutionalized to good effect.
The empire was much stronger than it had been in 450, but still needed the Long Wall and the Theodosian Wall to protect Constantinople, not against large‐scale invasions but rather against plunder raids from across the Danube.
The Sassanian empire of Persia remained the permanent strategic threat, undiminished by mutual respect, frequent negotiations, and formal treaties, including the ‘endless peace’ of 532. Persistent vigilance and a readiness to deploy reinforcements quickly were always necessary, if often insufficient, to contain Sassanian power in the Caucasus, across contested Armenia and the entire eastern front down to southern Syria. On the other hand, there was no longer any rival power north of Constantinople or beyond the Danube, while across the Adriatic the Ostrogothic kingdom of Italy desired good relations with the empire; at least some of its elite even wanted reunion under the empire. The Vandals and Alans who had conquered Africa in the last century were still there, but no longer threatened naval expeditions against Egypt. As for the dangers of the great Eurasian steppe, the nearest warlike nomads were the Turkic Kutrigurs in what is now Ukraine, at worst a nuisance rather than an irresistible force as Attila’s Huns had been.
More powerful steppe enemies were on their way, so it was more important that by the time of Justinian the warriors of the steppe had irreversibly lost their tactical superiority. The imperial army had undergone its tactical revolution, mastering the difficult technique of mounted archery with powerful composite reflex bows while retaining close‐combat skills with sword and thrusting lance. Even if their archery could not quite match the best that the Hun mercenaries with them could exhibit, Byzantine troopers could no longer be outclassed tactically. The steppe warriors had also lost much of their operational superiority, because the imperial army had adopted agile cavalry tactics, and what individual riders may have lacked in virtuoso horsemanship could be compensated by the greater resilience of their disciplined and cohesive units.
This also meant, of course, that the imperial army now had tactical and operational superiority over the Vandals and Alans of Africa and the Ostrogoths of Italy. The Alans were primarily horsemen; Vandals and Goths were formidable fighters at close quarters, fully capable of organizing major expeditions and not unskilled in sieges, but all now found themselves lacking in missile capability and battlefield mobility. Prokopios of Caesarea, who was there, reports how Belisarios, Justinian’s celebrated commander, explained the difference that made:
practically all the Romans and their allies, the Huns [Onogur mercenaries], are good mounted bowmen, but not a man among the Goths has had practice in this branch, for their horsemen are accustomed to use only spears and swords, while their archers enter battle on foot and under cover of the heavy‐armed men [to ward off cavalry charges]. So the horsemen, unless the engagement is at close quarters, have no means of defending themselves against opponents who use the bow, and therefore can easily be reached by the arrows and destroyed; and as for the foot‐soldiers, they can never be strong enough to make sallies against men on horseback.
This was only tactics, not strategy, but without this advantage it may be doubted whether Justinian would have embarked on his plan of reconquest, first of North Africa in 533–534 and then of Italy from 535.
Modern historians almost unanimously assert that he was excessively ambitious and that his conquests overextended the empire—true enough in retrospect, though only because of unforeseeable catastrophe. Not even his harshest critics consider Justinian a fool, or irrational, or incapable of sober calculation, but he was severely constrained by logistics. The inescapable fact was the impossibility of sending large armies by sea. In the biggest expedition, Belisarios set out from Constantinople to what is now Tunisia in the summer of 533 with some 10,000 infantry and 8,000 cavalry carried in 500 transport ships manned by 30,000 crewmen and escorted by ninety‐two war galleys. It was certainly a most impressive armada, but 18,000 soldiers were not enough to take on the Vandals and Alans in North Africa, let alone the Ostrogoths, whose fighting manpower was sustained by the resources of the whole of Italy.
It could only be done, and then only just, with the tactical and operational advantages of manoeuvre with forces of mounted bowmen: it also required a successful theatre strategy, and good generalship overall. Justinian was famously well served by talented field commanders, especially the eunuch Narses, who was perhaps the better tactician, and the more celebrated Belisarios of the many stratagems and ingenuities. Belisarios is still remembered today by unlettered Romans for his improvised floating mills powered by the current of the Tiber that ground corn into flour during the siege of 537–538. Successful stratagems are the classic force multipliers, and it was with Belisarios that they first became a Byzantine speciality, along with his systematic avoidance of attrition and maximum exploitation of manoeuvre.
In the record of both the Vandal and the Gothic wars left by his secretary Prokopios, an admirer but not uncritical, we read how Belisarios would undertake long marches on more perilous routes to avoid the expected direction, and reach instead the enemy’s flank or, better, his rear, and we read how he was willing to hazard the most risky stratagems to avoid direct assaults. To win with few against many, he replaced the mass he lacked with high‐pay‐off, high‐risk manoeuvres and bold surprise actions, coups de main that all would praise in the successful aftermath, but which were gambles indeed.
Stratagems aside, it was mostly its archery as well as good tactics that enabled the Byzantine army to defeat enemies with larger numbers quite regularly. In an authoritative reconstruction of two major battles of the Italian campaign, at Tadinae, or Busta Gallorum, on the Via Flaminia in what is now Umbria in 552, and at the River Casilinus, now Volturno, near Naples in 554, the Byzantine forces commanded by Narses included assorted foreign contingents of Lombards, Heruls, and even Persians. In both cases, it was the bowmen of the imperial army who made the critical difference in the crucial phase of the fight with their volleys of powerfully lethal arrows.
In sum, the army’s tactical and operational superiority was the sufficient condition for the two campaigns of North Africa and Italy; the necessary condition was the negotiated peace with the Sassanian Persians. Italy was hardly restored to a better condition (in melius convertere) by being liberated from the Ostrogoths in fighting that lasted until 552 through many destructive vicissitudes. From 568 the Lombard invasion started a new round of destructive fighting, which began only after Justinian’s death in 565, and long after the unforeseeable catastrophe that invalidated all his strategic plans.
Whatever the future held, Justinian achieved his ambitions almost in full. His forces conquered North Africa from Tunis through coastal Algeria to what is now the northern tip of Morocco, thus reaching the Atlantic; and, across the straits, a coastal slice of the Iberian peninsula in what is now south‐east Spain; all the islands of the western Mediterranean—the Balearics, Corsica, Sardinia, and Sicily; and all of Italy. Except for a tract of the Iberian coast and the southern coast of Gaul, where no rival naval power existed in any case, the entire Mediterranean was once again a Mare Nostrum, with none to contest the Byzantine navy.
Nor was this the achievement of a military adventurer, but merely the military dimension of even broader ambitions. Justinian was notoriously indefatigable, demonstrably very intelligent, unchallenged by rivals, and quite unfettered by conventions—he married a woman with the social status of an ex‐prostitute. He also had two more attributes that empowered him greatly: a full treasury at his accession, and a particular talent in finding the especially talented to serve him. Thus, Justinian could have been an even more successful version of Anastasios, who ruled for twenty‐seven years, built a great deal including the Long Wall and the fortress city of Dara, lost no wars, reduced taxes, yet supposedly left 320,000 pounds of gold in the treasury for his successor, Justin.
But Justinian had much larger aims. In the legal sphere, he set out to codify all the extant costitutiones, imperial pronouncements with the force of law. Theodosios II had also issued a codification, but it was incomplete, while Justinian’s code, already published in 529, which implies that it was started as soon as he gained the throne, collated all the costitutiones in the Theodosian code with those in two unofficial collections, adding more recent laws including his own to produce the Codex Iustinianus, in twelve books. The lawyer Tribonian was in charge, another of Justinian’s highly talented appointments. Tribonian was also the chief author of the Pandectae, Pandektes, or Digesta, the jurisprudential treatise that followed the Codex, which contains in fifty books the legal opinions on all manner of cases of thirty‐nine legal experts, notably Ulpian and Paulus. Once issued with official authority, the Digest became in effect an additional code of jurist‐made law, not dissimilar from the body of English common law—except that Romans were involved, hence the code is organized. Tribonian and his colleagues next produced a much shorter work, the Institutiones, in four books, a manual of legal training. By 534 the Codex Iustinianus was issued in a new edition with corrections and additions, including Justinian’s laws issued in the interim, and 168 new laws, novellae, mostly in Greek, were added by the time Justinian died in 565.
The sum total has been known since the sixteenth century as the Corpus Iuris Civilis. Long before then, by the end of the eleventh century, it was rediscovered in Italy and came to form the foundation of canon law, of secular legal studies at Bologna and of the first real university along with them, and of the Western jurisprudence that now extends worldwide. The continued use of untranslated Latin in English and even more in American courts—sine die, nolle prosequi, ad litem, res iudicata, etc.—symbolizes a much deeper persistence; these phrases all come from the Digesta of the Corpus Iuris Civilis.
Equally vast and equally successful was Justinian’s ambition in the realm of public works. Prokopios wrote an entire book, Peri Ktismaton (‘On Buildings’), to describe the churches, fortresses, and all else that Justinian built or enhanced—sometimes attributing to him the edifices of other emperors. But we know that under Justinian dozens of fortresses and other fortifications were built, or substantially rebuilt, in many parts of the empire, and that thirty‐nine churches were built or rebuilt in Constantinople alone, including the great church of Hagia Sophia, whose immense floating dome still amazes visitors, and whose design is reproduced with varying degrees of fidelity and felicity in thousands of churches all over the world. From the detailed description in Prokopios of how Hagia Sophia was built, we learn that the men chosen by Justinian in person to build a radically innovative building, Anthemios of Tralles and Isidore of Miletus, used mathematical engineering to calculate the statics of the delicately counter‐weighted dome. Once again the talented Justinian had found exceptional talents to realize his inordinate ambitions, and the evidence remains intact in Istanbul to prove that he was highly successful, just as it does in his ambitious jurisprudential project, whose influence is even wider now than it was at his death in 565.
So why were Justinian’s military ambitions different? That they were not grossly unrealistic we know from the simple fact that the maritime expedition sent in 533 to conquer Africa was neither shipwrecked nor defeated on arrival, so that what is now Tunisia and coastal Algeria were duly conquered. The conquest of Italy from the Ostrogoths, which started in 535, was a much more demanding undertaking, but it too was successfully completed in May 540, when Belisarios entered the Ostrogothic capital and last refuge of Ravenna to accept the surrender of King Witiges, or Vitigis, and his wife, Mathesuentha.
As noted, most modern historians hold that Justinian’s military ambitions were unrealistic, because they exceeded the capacity of the empire to sustain them. One year after Belisarios ceremoniously concluded his Italian war in May 540, because no powerful garrison remained in Italy to control them, the Goths were able to start fighting again, and with increasing success once Totila became their king. One established explanation is that Justinian did not reinforce Belisarios and his army because he was ‘afraid of the threat that a mighty general could pose’. Even Rome was lost in 546 to the Gothic counter‐offensive that persisted until 552. And because Sassanian Persia had repudiated the ‘endless peace’ treaty to resume fighting in 540, continuing with interruptions until 562, the empire had to sustain simultaneously two large‐scale wars on widely separated fronts, so that in 559 hardly any troops were left in Constantinople to fight off an incursion of Kutrigurs and Slavs. That was certainly evidence of overextension, and presaged an inability to defend the Danubian frontier and the Balkan peninsula with it, and therefore Greece also, from Avar invasions and Slav occupations.