Military activities
Justinian's reign was marked by the recovery of large stretches of land around the Western Mediterranean basin that had slipped out of imperial control in the 5th century. Although he never personally took part in military campaigns, he boasted of his successes in the prefaces to his laws and had them commemorated in art. The re-conquests were in large part carried out by his general Belisarius.
From his uncle, Justinian inherited ongoing hostilities with the Sasanian Empire. In 530 the Persian forces suffered a double defeat at Dara and Satala, but the next year saw the defeat of Roman forces under Belisarius near Callinicum. To counter the growing influence of the Persians in the Arabian Peninsula, Justinian occupied the Tiran Island and established a client network across the coast of Western Arabia, Central Arabia, and attempted to bring Himyar (the South Arabian kingdom) and Aksum (the Ethiopian kingdom) under his sway. However, his attempts to make alliances with the Axumites of Ethiopia and the Himyarites of Yemen against the Persians failed. When the Sasanian emperor Kavad I died in September 531, Justinian concluded an "Eternal Peace" (which cost him 11,000 pounds of gold) with his successor Khosrau I (532). Having thus secured his eastern frontier, Justinian turned his attention to the West, where Germanic peoples had established kingdoms in the territories of the former Western Roman Empire.
The first of the western kingdoms Justinian attacked was that of the Vandals in North Africa. King Hilderic, who had maintained good relations with Justinian and the North African Catholic clergy, had been overthrown by his cousin Gelimer in 530. Imprisoned, the deposed king appealed to Justinian. Justinian protested Gelimer's actions, demanding that Gelimer return the kingdom to Hilderic. Gelimer replied, in effect, that Justinian had no authority to make these demands. Angered at this response, Justinian quickly concluded his ongoing war with the Sasanians and prepared an expedition against the Vandals in 533.
In 533, Belisarius sailed to Africa with a fleet of 92 dromons, escorting 500 transports carrying an army of about 15,000 men, as well as a number of barbarian troops. They landed at Caput Vada (now Ras Kaboudia, now in Chebba in Tunisia). They defeated the Vandals, who were caught completely off guard, at Ad Decimum on 14 September 533 and Tricamarum in December; Belisarius took Carthage. King Gelimer fled to Mount Pappua in Numidia, but surrendered the next spring. He was taken to Constantinople, where he was paraded in a Triumph. Sardinia and Corsica, the Balearic Islands, and the stronghold of Septem Fratres (now Ceuta) near the Rock of Gibraltar (Latin Mons Calpe) were recovered in the same campaign.
In this war, the contemporary Procopius remarks that the coastal region of North Africa known in Latin as 'Africa' was so entirely depopulated that a person might travel several days without meeting a human being, and he adds, "it is no exaggeration to say, that in the course of the war 5,000,000 perished by the sword, and famine, and pestilence." However, JAS Evans casts doubt on Procopius' claims, and asserts that there was a large building program following the conquest, and despite periods of unrest, Africa was generally flourishing. A praetorian prefecture of Africa, centred in Carthage, was established in April 534, but it would teeter on the brink of collapse during the next 15 years, amidst warfare with the Mauri and military mutinies. By the mid-540s, under a succession of Byzantine generals, the region was disrupted under civil war, plague and military campaigning. The area was not completely pacified until 548, but remained peaceful thereafter and enjoyed a measure of prosperity. The recovery of Africa cost the empire about 100,000 pounds of gold.
As in Africa, dynastic struggles in the Amal dynasty ruling the Ostrogothic Kingdom of Italy and the northern Balkans provided an opportunity for intervention. The young king Athalaric had died on 2 October 534, and a usurper, Theodahad, had imprisoned queen Amalasuintha, Theodoric's daughter and mother of Athalaric, on the island of Martana in Lake Bolsena, where he had her assassinated in 535. Thereupon Belisarius, with 7,500 men, invaded Sicily (535) and advanced into Italy, sacking Naples and capturing Rome on 9 December 536. By that time Theodahad had been deposed by the Ostrogothic army, who had elected Vitiges as their new king. He gathered a large army and besieged Rome from February 537 to March 538 without being able to retake the city.
Justinian sent another general, Narses, to Italy, but tensions between Narses and Belisarius hampered the progress of the campaign. Milan (Mediolanum) was taken, but was soon recaptured and razed by the Ostrogoths. Justinian recalled Narses in 539. By then the military situation had turned in favour of the Romans, and in 540 Belisarius laid siege to the capital of Ravenna. There he was offered the title of Western Roman Emperor by the Ostrogoths at the same time envoys of Justinian were arriving to negotiate a peace that would leave the region north of the Po in Gothic hands. Belisarius feigned acceptance of the offer, entered the city in May 540, and reclaimed it for the Empire. Then, having been recalled by Justinian, Belisarius returned to Constantinople, taking the captured Vitiges and his queen Mataswintha with him.
Belisarius had been recalled in the face of renewed hostilities by the Persians. Following a revolt against the Empire in Armenia in the late 530s and possibly motivated by the pleas of Ostrogothic ambassadors, King Khosrau I broke the "Eternal Peace" and invaded Roman territory in the spring of 540. He first sacked Beroea and then Antioch (allowing the garrison of 6,000 men to leave the city), besieged Daras, and then went on to attack the Byzantine base in the small but strategically significant satellite kingdom of Lazica near the Black Sea as requested by its discontented king Gubazes, exacting tribute from the towns he passed along his way. He forced Justinian I to pay him 5,000 pounds of gold, plus 500 pounds of gold more each year.
Belisarius arrived in the East in 541, but after some success, was again recalled to Constantinople in 542. The reasons for his withdrawal are not known, but it may have been instigated by rumours of his disloyalty reaching the court. The outbreak of the plague coupled with a rebellion in Persia brought Khosrow I's offensives to a halt. Exploiting this, Justinian ordered all the forces in the East to invade Persian Armenia, but the 30,000-strong Byzantine force was defeated by a small force at Anglon. The next year, Khosrau unsuccessfully besieged the major city of Edessa. Both parties made little headway, and in 545 a truce was agreed upon for the southern part of the Roman-Persian frontier. After that, the Lazic War in the North continued for several years: the Lazic king switched to the Byzantine side, and in 549 Justinian sent Dagisthaeus to recapture Petra, but he faced heavy resistance and the siege was relieved by Sasanian reinforcements. Justinian replaced him with Bessas, who was under a cloud after the loss of Rome in 546, but he managed to capture and dismantle Petra in 551. The war continued for several years until a second truce in 557, followed by a fifty years' peace in 562. Under its terms, the Persians agreed to abandon Lazica in exchange for an annual tribute of 400 or 500 pounds of gold (30,000 solidi) to be paid by the Romans.
While military efforts were directed to the East, the situation in Italy took a turn for the worse. Under their respective kings Ildibad and Eraric (both murdered in 541) and especially Totila, the Ostrogoths made quick gains. After a victory at Faenza in 542, they reconquered the major cities of Southern Italy and soon held almost the entire Italian Peninsula. Belisarius was sent back to Italy late in 544 but lacked sufficient troops and supplies. Making no headway, he was relieved of his command in 548. Belisarius succeeded in defeating a Gothic fleet of 200 ships. During this period the city of Rome changed hands three more times, first taken and depopulated by the Ostrogoths in December 546, then reconquered by the Byzantines in 547, and then again by the Goths in January 550. Totila also plundered Sicily and attacked Greek coastlines.
Finally, Justinian dispatched a force of approximately 35,000 men (2,000 men were detached and sent to invade southern Visigothic Hispania) under the command of Narses. The army reached Ravenna in June 552 and defeated the Ostrogoths decisively within a month at the battle of Busta Gallorum in the Apennines, where Totila was slain. After a second battle at Mons Lactarius in October that year, the resistance of the Ostrogoths was finally broken. In 554, a large-scale Frankish invasion was defeated at Casilinum, and Italy was secured for the empire, though it would take Narses several years to reduce the remaining Gothic strongholds. At the end of the war, Italy was garrisoned with an army of 16,000 men. The recovery of Italy cost the empire about 300,000 pounds of gold.
In addition to the other conquests, the Empire established a presence in Visigothic Hispania, when the usurper Athanagild requested assistance in his rebellion against King Agila I. In 552, Justinian dispatched a force of 2,000 men; according to the historian Jordanes, this army was led by the octogenarian Liberius. The Byzantines took Cartagena and other cities on the southeastern coast and founded the new province of Spania before being checked by their former ally Athanagild, who had by now become king. This campaign marked the apogee of Byzantine expansion.
During Justinian's reign, the Balkans suffered from several incursions by the Turkic and Slavic peoples who lived north of the Danube. Here, Justinian resorted mainly to a combination of diplomacy and a system of defensive works. In 559 a particularly dangerous invasion of Sklavinoi and Kutrigurs under their khan Zabergan threatened Constantinople, but they were repulsed by the aged general Belisarius.
Justinian's ambition for re-conquest was only partly realized, with the only lasting and sustainable conquest being Africa. In the West, the early military successes of the 530s were followed by years of stagnation. The dragging war with the Goths was a disaster for Italy, even though its long-lasting effects may have been less severe than is sometimes thought. The heavy taxes that the administration imposed upon the Italian population were deeply resented.
The final victory in Italy and the conquest of Africa and the coast of southern Hispania significantly enlarged the area of Byzantine influence and eliminated all naval threats to the empire, which in 555 reached its territorial zenith. Despite losing much of Italy soon after Justinian's death, the empire retained several important cities, including Rome, Naples, and Ravenna, leaving the Lombards as a regional threat. The newly founded province of Spania kept the Visigoths as a threat to Hispania alone and not to the western Mediterranean and Africa.
Events of the later years of his reign showed that Constantinople itself was not safe from barbarian incursions from the north, and even the relatively benevolent historian Menander Protector felt the need to attribute the Emperor's failure to protect the capital to the weakness of his body in his old age. Some historians view that in his efforts to renew the Roman Empire, Justinian dangerously stretched its resources while failing to take into account the changed realities of 6th-century Europe.
With regard to the long term consequences of Justinian's conquests, the provinces of Italy, North Africa and Spain were some of the wealthiest provinces of the Roman Empire, and thus it would not be unreasonable to assume that those provinces would make a substantial contribution to the empire's coffers given that these provinces were highly taxable. Peter Sarris suggests that Justinian's efforts were hampered by the plague and as a result it made reconquering the West harder and costlier. According to some historians, despite the scale of destruction caused by the conquests, North Africa and Southern Italy generally paid for themselves and yielded substantial profit for the empire. The conquests in the West also expanded Byzantine influence over the papacy and added a source of Germanic warriors for recruitment in the army.
