From the death of Constantine in 337 until the birth of Mohammad in 570, enormous changes occurred in both the Roman Empire and Christianity. At his death, Constantine was sole emperor of the entire Roman Empire. Both the Western and Eastern portions of the empire were under constant pressure from Barbarian Tribes invading from the north. The eastern part of the empire also had to deal with the Persian Empire. After the death of the emperor Theodosius in 395, the empire was again divided into two distinct entities under his sons, Arcadius in the east and Honorius in the west.
The western empire fared poorly under relentless pressure from the north. Rome itself was sacked in 410 by Alaric the Goth and again in 455 by the vandals led by Genseric. The last Roman emperor of the west, Romulus “Augustulus” (Little Augustus), was deposed by the German, Otoacer, in 476. Fortunately, by that time, most of the Barbarian Tribes of Europe have been converted to Christianity. However, after the Western Roman Empire had been destroyed, the church remained and the people turned to the bishop of Rome for guidance and instruction in Christianity. Ultimately, the bishop of Rome became known as the father of the church or the pope.
The Eastern empire fared better than that in the west. It actually lasted over 1,000 years until the fall of Constantinople in 1453. It also suffered attacks by Barbarian Tribes from the north. A Roman army led by the emperor of Valens was decisively defeated by the Goths in the battle of Adrianople in 378, in which Valens was himself killed. Valens was succeeded by Theodosius who stabilized the eastern empire more by diplomacy than by force of arms and reached an agreement with the Goths. Nevertheless, by 402, the Goths were again on the march led by probably their most outstanding general, Alaric. They were defeated in 402 by the Roman General, Stilicho, and did not seriously threaten the eastern empire again, although Alaric, as previously noted, attacked and sacked Rome in 410. The other major threat to the Roman Empire were the Huns and their leader Attila who inflicted a serious defeat at Gallipoli in 447 upon the Byzantines, as the Romans of the east were becoming known. After being essentially bought off by Theodosius, they then turned their attention to the west.
After the death of Theodosius in 450, Byzantium came under constant pressure from the east by the Persian Empire. A three-year war was fought with Persia around 312, resulting in the loss of several provinces. In 527, Justinian began his 38-year reign. He was not popular, but had many great achievements. Under the leadership of his great general, Belisarius, the Persians under their king, Chosroes, were defeated in 532 and the lost territories regained. He also reunited the Roman and Eastern churches, published Justinian’s code, and dealt with the heresies that were causing dissention in Christianity. Africa was conquered in 533, the Goths driven out of Italy in 546, and another attack on Constantinople by the Goths repulsed in 559.
The major problem for Christianity during the reign of Justinian and his predecessors was the persistence of numerous heresies which continued to proliferate. Despite the council of Nicea in 325 and the council of Chalcedon in 451. The latter council was called by the emperor, Marcian, and was attended by hundreds of bishops from both east and west. It condemned Arianism, Monophytism, and Nestorism and affirmed the doctrine that Christ is one person with two natures, inseparably united in a perfect God and a perfect man, which is what Christians believe today. Arianism, which was previously described, placed Christ separately between father and man, inferior to the former and superior to the latter. This was very prevalent in the Western empire. Nestorism taught that Christ was not a single person, but possessed two distinct persons, both man and divine. This was a common heresy in the east. Monophytism believed that the Christ possessed a single nature, which was divine. This heresy was very worrisome to the orthodox Catholic Church because it was rapidly spreading, especially in Egypt and Africa. Fortunately, for the church, both the emperor and the pope were staunched orthodox Catholics. However, they were unable to completely stamp out the heretical beliefs. Justinian finally called for another council in Constantinople in 553, which confirmed the findings of the previous two councils and resulted in finally beginning to suppress the heresies in favor of the orthodox view of the Trinity. Today, there are still some people who adhere to the heretical beliefs, but they are few in number.
At the end of the sixth century, the eastern Roman Empire or Byzantium was still the dominant power in the Mediterranean world. It was bordered on the east by the Persian Empire. However, Byzantium controlled the Balkans, Asia Minor, Greece, the Greek islands, including Cypress and Crete, Palestine, Syria, and part of North Africa.
The Western Roman Empire was now divided among the various formerly Barbarian Tribes, which were now fortunately Christianized. Italy was taken by the eastern Goths (Ostrogoths) who settled among the native inhabitants. Southern France and northern Spain were occupied by the western Goths (Visigoths). Southern Spain and North Africa were taken over by the Vandals and the Burgundians were in eastern France. All of these tribes were Christian, although they were mostly Arians.
The Franks occupied northern France, Belgium, and the southern part of the Netherlands, the Frisians were in the northern Netherlands, the Saxons in the rest of the Netherlands, and the Anglo Saxons in Britain. All of these were still pagan Barbarians. This was the world into which Mohammed was born around 570.
The Arabian Peninsula was inhabited primarily by nomadic Arabs engaged in commerce and regularly sending caravans both to the east and west. Most of the activity was along the coast, but there were two commercial centers in the interior, Mecca and Medina. The kingdoms of Yemen and Abyssinia were in the south and they both contended for domination of the area. Politics were tribal and controlled by the most powerful families. It was into one of the strongest of these that Mohammed was born. In his early life, he was orphaned and raised by relatives and was therefore able to participate in commerce and travel with the caravans to Syria and Yemen. Mohammad was always religious, but did not devote himself to it until after he married a wealthy widow around 590. Mohammed had his first vision around 610 and began to preach the new religion of Islam. Unfortunately, his wife and his uncle, who was a leader of Mohammed’s own Clan, both died in 619 and resistance to his teaching increased in Mecca after the loss of these protectors. Medina was a city to the north of Mecca which was having internal problems and appealed to Mohammed to migrate there and provide leadership. In 622, he and his followers did so and this was called the Hegira. This began a war between the two cities which culminated in the submission of Mecca to Islam in 629. In 630, Mohammed attacked the Byzantine and Persian empires with great success. He died in 632 and was succeeded by his father-in-law, Abu Bakr, who died in 634 after consolidating Islam in Arabia and the conquered Persian and Byzantine provinces. He was succeeded by Mohammed’s son-in-law, Omar, who ruled for ten years. During that time, Islam expanded rapidly. The Persian Empire, Palestine, and Syria were quickly conquered (635-638). Later, western expansion included Egypt and North Africa, as far as Tunisia (648). Later in that century and in the early eighth century, Islamic conquest included the rest of North Africa, Spain, and Southern France. The Arabs were finally defeated at the Battle of Tours in 732 by a combined Christian army led by Charles, the king of the Franks, later known as Charles Martel or Charles the Hammer.
Despite becoming the predominate religion of the entire Roman Empire, Christianity still faced many existential problems during those early centuries. In the west, the invading pagan Barbarian Tribes from Northern and Eastern Europe were held in bay by the empire until they had been Christianized by missionaries. When they finally overran Western Europe and Italy, they had by then become Christians and firmly established the church in those lands. If the Western Roman Empire had not held out until the fifth century and fallen sooner, these tribes would have remained Pagan and unable to later repulse Islam.
The eastern Byzantine Empire defeated the tribes attacking from the north and thus preserved Christianity in the east. Byzantium was then able to withstand the Islamic invaders from the south for almost 1,000 years until it too fell in 1453 to the Islamic Ottoman Turks. The important fact is that the Balkans, Greece, and Southern Europe were protected by the Byzantine Empire from Islam for most of those centuries. This enabled the Christian nations of Europe to finally unite to stop Islamic conquest by defeating them at Vienna in 1683.
Finally, the conservative orthodox Catholic view of the nature of the Trinity prevailed over all the heresies which evolved during those early centuries. This occurred primarily because of the steadfast adherence of the emperors, both east and west, and the pope to the true faith as taught by the apostles and their disciples.
The Roman Empire was finally gone, but its influence on Christianity will persist as long as the church exists. God used the Roman Empire to allow Christianity to survive, grow, and ultimately dominate the western world.