Next was the Imperial reconquest of Italy, which while brutal and drawn-out, seemed to have been accomplished by 552 with the defeat of Teias near Pompei. Even so, 540 was the turning point. Imperial prestige had been restored at home as the Blues and Greens had been repressed, and North Africa as well as Italy had been restored to Roman control. Now, Justinian's (d. 565) last decades would prove a continuous ordeal. It began in March 540, when Sassanian Shah Chosroes I began a major offensive into Eastern Imperial lands. Moving through Syria, Persian forces took the holy Christian city of Antioch, pillaging it severely in June 540. Though Justinian agreed to terms including more tribute, Chosroes' armies continued to ravage through Asia Minor. A huge Byzantine army was defeated in Armenia in 543. Still, by the end of the decade, Persian forces had been fought to a standstill. Though peace was not made, it did demonstrated that 1) Eastern Roman forces still possessed military prowess, and 2) neither Romans nor Sassanians could ever sustainably extend their power beyond central Iraq.
At the same time as Persian wars and resurgent Ostrogoths in Italy, a pressing Balkan crisis erupted. After the Germanic migrations and Hun collapse of the 380s-450s, two new Barbarian groups began to move in from the North and East. The first was the Bulgars, a nomadic group from the Ukraine perhaps related to the Huns. They grouped into two subunits, the Utrigurs in the East, and the Kutrigurs in the West. The second major Barbarian group was the Slavs. A forest people in the woods east of original German settlement areas, they had moved to the lower Danube when the Huns fell. Their level of barbarity made the Germans look civilized. Pagans, they had no visible government structures, and though they began raiding Imperial territories from the 500s, they were not so dangerous, and new walls prevented tremendous damage. In the 540s, though, Slav raids increased dramatically, now under the leadership of the equally plunder- thirsty Bulgars. They were able to range into Thrace as far as southern Greece, and with Roman troops committed in East and West, there was little offensive action possible. Instead, Justinian built three chains of east-west fortifications, which would cause Slavic-Bulgar losses upon their return from plundering. In the long term, this did cut down on Barbarian incursions.
This same decade witnessed terrible natural disaster. In 542 a plague struck the cities of the Mediterranean basin, affecting all the settled, urban population. Its rate of mortality was staggering--up to 40% of those who contracted it. It may have been the Bubonic Plague, based on a bacillus which infects rats. Indigenous to rodent kingdoms in Central Africa and the China-Tibet border, it rarely spread from these areas given its virulence and need for immense host populations. But when a rodent happened to stow away on a caravan or sea vessel, it did spread. It first appeared in Pelusium in Egypt, then spread in all Mediterranean directions, especially to port cities. After the 541-42 outbreak, Constantinople saw two more plague crises over intervals of fifty years. As many as 10,000 people may have died a day. Justinian himself was near death in 543. The disease reduced tremendously the state and society's resources in warding off Persians and Goths, who were also affected by the illness, as well as the Bulgars and Slavs, who were less urban, less Mediterranean, had lower population densities, and as a result were most likely much less susceptible to the epidemic.
A theological dispute also complicated matters, alienating Western clerics at the very time their support was necessary in the Italian campaigns. An extreme Monophysite called Jacob Baradaeus had been made bishop by the exiled Alexandria Patriarch in 543, after which he roamed through Mesopotamia, the Levant, and Asia Minor consecrating bishops and thousands of Monophysite priests. Justinian had to do something, but did not want to alienate Monophysites in the Empire's current conditiion. He therefore decided to publicly condemn Nestorians, whom everyone disliked and whose numbers were few. This satisfied no one, and an east-west frenzy of excommunications lasted for the next ten years. Only after the defeat of the Goths was Justinian able to discipline Pope Vigilus, who was forced to withdraw all of his condemnations of the Eastern Church.
After the final defeat of the Ostrogoths, during which North African revolts had proven troublesome, there was one more success. An insurrection in Visigothic Spain allowed a small force sent by Justinian to occupy a small sector of southern Spain, giving Constantinople a toe-hold on all parts of the Mediterranean Roman core. Still, the Emperor's last years were difficult. In the late 550s, the Persian war re-ignited, while in 559, the Kutrigur Bulgars led most of the Slavs over the Danube and pillaged into the Balkans. Faithful Belisarius was able to draw them far south, cutting off retreat with a naval fleet. Then Byzantine diplomacy was able to engineer a Kutrigur-Utrigur split, with the latter defeating their western brothers. The Bulgars and Slavs then withdrew, and in 561, the Persians declared a fifty-year truce. At his death, Justinian left an enlarged Empire more superficially magnificent, but with severe shortages in funds and human/military resources while its commitments were exceedingly broad.
In Justinian we have the last Emperor of the Latin, Roman mould. He was from Thrace, and while he was a native Latin speaker, his Greek was very poor. Further, initiatives such as the Law Code show that he perceived himself totally as a continuation of Roman rule going back to the first century. Of course, an alternative interpretation is that he and his advisers felt the necessity of codifying a body of law and custom no longer able to evolve under new circumstances. Still and all, we should see Justinian as the last Latin Emperor in Constantinople, though he faced dilemmas characteristic of the Byzantine period, and left a state and society of a very different, medieval sort.