Tetrarchy

Greek is an independent branch of the Indo-European family of languages, native to Greece, Cyprus, southern Italy, southern Albania, and other regions of the Balkans, the Black Sea coast, Asia Minor, and the Eastern Mediterranean. It has the longest documented history of any Indo-European language, spanning at least 3,400 years of written records. Its writing system is the Greek alphabet, which has been used for approximately 2,800 years; previously, Greek was recorded in writing systems such as Linear B and the Cypriot syllabary. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic, and many other writing systems.

Gaius Plinius Secundus, called Pliny the Elder, was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic Naturalis Historia, which became an editorial model for encyclopedias. He spent most of his spare time studying, writing, and investigating natural and geographic phenomena in the field.

Flavius Claudius Constantius Gallus (326–354) was a statesman and ruler in the eastern provinces of the Roman Empire from 351 to 354, as Caesar under emperor Constantius II, his cousin. A grandson of emperor Constantius Chlorus and empress Flavia Maximiana Theodora, and a son of Julius Constantius and Galla, he belonged to the Constantinian dynasty. He was born during the reign of his uncle Constantine the Great, and was among the few to survive the killings of male members of the imperial family in 337. Under Constantius II, he married Constantina, Constantine's daughter and Constantius' sister. As Caesar he dealt with a Jewish revolt (351–352) and ruled from Antioch, but the emperor came to mistrust him, and ultimately had him executed and replaced with his younger half-brother Julian.

Lucius Caecilius Firmianus signo Lactantius was an early Christian author who became an advisor to Roman emperor Constantine I, guiding his Christian religious policy in its initial stages of emergence, and a tutor to his son Crispus. His most important work is the Institutiones Divinae, an apologetic treatise intended to establish the reasonableness and truth of Christianity to pagan critics.

Edward Gibbon was an English historian, writer, and member of parliament. His most important work, The History of the Decline and Fall of the Roman Empire, published in six volumes between 1776 and 1788, is known for the quality and irony of its prose, its use of primary sources, and its polemical criticism of organised religion.

Christian Matthias Theodor Mommsen was a German classical scholar, historian, jurist, journalist, politician and archaeologist. He is widely regarded as one of the greatest classicists of the 19th century. His work regarding Roman history is still of fundamental importance for contemporary research. He received the 1902 Nobel Prize in Literature for being "the greatest living master of the art of historical writing, with special reference to his monumental work, A History of Rome", after having been nominated by 18 members of the Prussian Academy of Sciences. He was also a prominent German politician, as a member of the Prussian and German parliaments. His works on Roman law and on the law of obligations had a significant impact on the German civil code.

Otto Karl Seeck was a German classical historian who is perhaps best known for his work on the decline of the ancient world. He was born in Riga.

The argenteus was a silver coin produced by the Roman Empire from the time of Diocletian's coinage reform in AD 294 to ca. AD 310. It was of similar weight and fineness to the denarius of the time of Nero. The coin was produced at a theoretical weight of 1/96th of a Roman pound, as indicated by the Roman numeral XCVI on the coin's reverse.

Antioch on the Orontes was a Hellenistic city founded by Seleucus I Nicator in 300 BC. The city served as the capital of the Seleucid Empire and later as regional capital to both the Roman and Byzantine Empire. During the Crusades, Antioch served as the capital of the Principality of Antioch, one of four Crusader states that were founded in the Levant. Its inhabitants were known as Antiochenes. The modern city of Antakya, in Hatay Province of Turkey, was named after the ancient city, which lies in ruins on the Orontes River and did not overlap in habitation with the modern city.

Diarchy, duarchy, or duumvirate is a form of government characterized by corule, with two people ruling a polity together either lawfully or de facto, by collusion and force. The leaders of such a system are usually known as corulers.

Maximian, nicknamed Herculius, was Roman emperor from 286 to 305. He was Caesar from 285 to 286, then Augustus from 286 to 305. He shared the latter title with his co-emperor and superior, Diocletian, whose political brain complemented Maximian's military brawn. Maximian established his residence at Trier but spent most of his time on campaign. In late 285, he suppressed rebels in Gaul known as the Bagaudae. From 285 to 288, he fought against Germanic tribes along the Rhine frontier. Together with Diocletian, he launched a scorched earth campaign deep into Alamannic territory in 288, refortifying the frontier.

Caesar is a title of imperial character. It derives from the cognomen of Julius Caesar, a Roman dictator. The change from being a familial name to a title adopted by the Roman emperors can be traced to AD 68, following the fall of the Julio–Claudian dynasty.

Diocletian, nicknamed "Jovius", was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. Diocles rose through the ranks of the military early in his career, eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name Diocletianus. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Galerius Valerius Maximianus was Roman emperor from 305 to 311. During his reign he campaigned, aided by Diocletian, against the Sasanian Empire, sacking their capital Ctesiphon in 299. He also campaigned across the Danube against the Carpi, defeating them in 297 and 300. Although he was a staunch opponent of Christianity, Galerius ended the Diocletianic Persecution when he issued an Edict of Toleration in Serdica in 311.

A barbarian, or savage, is someone who is perceived to be either uncivilized or primitive. The designation is usually applied as a generalization based on a popular stereotype; barbarians can be members of any nation judged by some to be less civilized or orderly but may also be part of a certain "primitive" cultural group or social class both within and outside one's own nation. Alternatively, they may instead be admired and romanticised as noble savages. In idiomatic or figurative usage, a "barbarian" may also be an individual reference to a brutal, cruel, warlike, and insensitive person.

The Rhine is one of the major European rivers. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps. It forms part of the Swiss-Liechtenstein, Swiss-Austrian, and Swiss-German borders. After that the Rhine defines much of the Franco-German border, after which it flows in a mostly northerly direction through the German Rhineland. Finally in Germany the Rhine turns into a predominantly westerly direction and flows into the Netherlands where it eventually empties into the North Sea. It drains an area of 9,973 sq km and its name derives from the Celtic Rēnos. There are also two German states named after the river, North Rhine-Westphalia and Rhineland-Palatinate.

The Danube is the second-longest river in Europe, after the Volga in Russia. It flows through much of Central and Southeastern Europe, from the Black Forest into the Black Sea. A large and historically important river, it was once a frontier of the Roman Empire and today connects ten European countries, running through their territories or being a border. Originating in Germany, the Danube flows southeast for 2,850 km (1,770 mi), passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova, and Ukraine. Among the many cities on the river are four national capitals: Vienna, Budapest, Belgrade and Bratislava. Its drainage basin amounts to 817 000 km² and extends into nine more countries.

The praefectus urbanus, also called praefectus urbi or urban prefect in English, was prefect of the city of Rome, and later also of Constantinople. The office originated under the Roman kings, continued during the Republic and Empire, and held high importance in late Antiquity. The office survived the collapse of the Western Roman Empire, and the last urban prefect of Rome, named Iohannes, is attested in 599. In the East, in Constantinople, the office survived until the 13th century.

Nicomedia was an ancient Greek city located in what is now Turkey. In 286, Nicomedia became the eastern and most senior capital city of the Roman Empire, a status which the city maintained during the Tetrarchy system (293–324).

Sirmium was a city in the Roman province of Pannonia, located on the Sava river, on the site of modern Sremska Mitrovica in the Vojvodina autonomous provice of Serbia. First mentioned in the 4th century BC and originally inhabited by Illyrians and Celts, it was conquered by the Romans in the 1st century BC and subsequently became the capital of the Roman province of Pannonia Inferior. In 294 AD, Sirmium was proclaimed one of four capitals of the Roman Empire. It was also the capital of the Praetorian prefecture of Illyricum and of Pannonia Secunda. The site is protected as an archaeological Site of Exceptional Importance. The modern region of Syrmia was named after the city.

Sremska Mitrovica is a city and the administrative center of the Srem District in the autonomous province of Vojvodina, Serbia. It is situated on the left bank of the Sava river. As of 2011, the city has a total population of 37,751 inhabitants, while its administrative area has a population of 79,940 inhabitants.

Serbia, officially the Republic of Serbia, is a landlocked country in Southeastern and Central Europe, situated at the crossroads of the Pannonian Basin and the Balkans. It shares land borders with Hungary to the north, Romania to the northeast, Bulgaria to the southeast, North Macedonia to the south, Croatia and Bosnia and Herzegovina to the west, and Montenegro to the southwest, and claims a border with Albania through the disputed territory of Kosovo. Serbia without Kosovo has about 6.7 million inhabitants, about 8.4 million if Kosovo is included. Its capital Belgrade is also the largest city.

Belgrade is the capital and largest city of Serbia. It is located at the confluence of the Sava and Danube rivers and at the crossroads of the Pannonian Plain and the Balkan Peninsula. The population of the Belgrade metropolitan area is 1,685,563, according to the 2022 census. It is the third most populated of all cities on the Danube river.

Mediolanum, the ancient city where Milan now stands, was originally an Insubrian city, but afterwards became an important Roman city in northern Italy. The city was settled by the Insubres around 600 BC, conquered by the Romans in 222 BC, and developed into a key centre of Western Christianity and informal capital of the Western Roman Empire. It declined under the ravages of the Gothic War, its capture by the Lombards in 569, and their decision to make Ticinum the capital of their Kingdom of Italy.

Milan is a city in northern Italy, capital of Lombardy, and the second-most populous city proper in Italy after Rome. The city proper has a population of about 1.4 million, while its metropolitan city has 3.26 million inhabitants. Its continuously built-up urban area is the fourth largest in the EU with 5.27 million inhabitants. According to national sources, the population within the wider Milan metropolitan area, is estimated between 8.2 million and 12.5 million making it by far the largest metropolitan area in Italy and one of the largest in the EU.

Aquileia is an ancient Roman city in Italy, at the head of the Adriatic at the edge of the lagoons, about 10 kilometres (6 mi) from the sea, on the river Natiso, the course of which has changed somewhat since Roman times. Today, the city is small, but it was large and prominent in classical antiquity as one of the world's largest cities with a population of 100,000 in the 2nd century AD and is one of the main archaeological sites of northern Italy. In late antiquity the city was the first city in the Italian Peninsula to be sacked by Attila the Hun.

Aurelian was a Roman emperor, who reigned during the Crisis of the Third Century, from 270 to 275. As emperor, he won an unprecedented series of military victories which reunited the Roman Empire after it had nearly disintegrated under the pressure of barbarian invasions and internal revolts. Born in modest circumstances, near the Danube River, he entered the Roman army in 235 and climbed up the ranks. He went on to lead the cavalry of the emperor Gallienus, until Gallienus' assassination in 268. Following that, Claudius Gothicus became emperor until his own death in 270. Claudius' brother Quintillus ruled the empire for three months, before Aurelian became emperor.

The Sasanian Empire, officially known as Eranshahr was the last Iranian empire before the early Muslim conquests of the 7th–8th centuries AD. Named after the House of Sasan, it endured for over four centuries, from 224 to 651 AD, making it the longest-lived Persian imperial dynasty. The Sasanian Empire succeeded the Parthian Empire, and re-established the Persians as a major power in late antiquity alongside its neighbouring arch-rival, the Roman Empire.

Narseh was the seventh Sasanian King of Kings of Iran from 293 to 303.

Allectus was a Roman-Britannic usurper-emperor in Britain and northern Gaul from 293 to 296.

Lucius Domitius Domitianus or, rarely, Domitian III, was a Roman usurper against Diocletian, who seized power for a short time in Egypt.

Egypt, officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediterranean Sea to the north, the Gaza Strip of Palestine and Israel to the northeast, the Red Sea to the east, Sudan to the south, and Libya to the west. The Gulf of Aqaba in the northeast separates Egypt from Jordan and Saudi Arabia. Cairo is the capital and largest city of Egypt, while Alexandria, the second-largest city, is an important industrial and tourist hub at the Mediterranean coast. At approximately 100 million inhabitants, Egypt is the 14th-most populated country in the world.

The Civil Wars of the Tetrarchy were a series of conflicts between the co-emperors of the Roman Empire, starting in 306 AD with the usurpation of Maxentius and the defeat of Severus and ending with the defeat of Licinius at the hands of Constantine I in 324 AD.

Galerius Valerius Maximinus, born as Daza, was Roman emperor from 310 to 313. He became embroiled in the Civil wars of the Tetrarchy between rival claimants for control of the empire, in which he was defeated by Licinius. A committed pagan, he engaged in one of the last persecutions of Christians, before issuing an edict of tolerance near his death.

The Battle of the Milvian Bridge took place between the Roman Emperors Constantine I and Maxentius on 28 October 312. It takes its name from the Milvian Bridge, an important route over the Tiber. Constantine won the battle and started on the path that led him to end the Tetrarchy and become the sole ruler of the Roman Empire. Maxentius drowned in the Tiber during the battle; his body was later taken from the river and decapitated, and his head was paraded through the streets of Rome on the day following the battle before being taken to Africa.

Raffaello Sanzio da Urbino, better known as Raphael, was an Italian painter and architect of the High Renaissance. His work is admired for its clarity of form, ease of composition, and visual achievement of the Neoplatonic ideal of human grandeur. Together with Leonardo da Vinci and Michelangelo, he forms the traditional trinity of great masters of that period.

Constantine I, also known as Constantine the Great, was Roman emperor from AD 306 to 337, the first one to convert to Christianity. Born in Naissus, Dacia Mediterranea, he was the son of Flavius Constantius, a Roman army officer of Illyrian origin who had been one of the four rulers of the Tetrarchy. His mother, Helena, was a Greek Christian of low birth. Later canonized as a saint, she is traditionally attributed with the conversion of her son. Constantine served with distinction under the Roman emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces before being recalled in the west to fight alongside his father in Britain. After his father's death in 306, Constantine became emperor. He was acclaimed by his army at Eboracum, and eventually emerged victorious in the civil wars against emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.

Marcus Aurelius Valerius Maxentius was a Roman emperor, who reigned from 306 until his death in 312. Despite ruling in Italy and North Africa, and having the recognition of the Senate in Rome, he was not recognized as a legitimate emperor by his fellow emperors.

Valerius Licinianus Licinius was Roman emperor from 308 to 324. For most of his reign he was the colleague and rival of Constantine I, with whom he co-authored the Edict of Milan, AD 313, that granted official toleration to Christians in the Roman Empire. He was finally defeated at the Battle of Chrysopolis, and was later executed on the orders of Constantine I.

Diocletian, nicknamed "Jovius", was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. Diocles rose through the ranks of the military early in his career, eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name Diocletianus. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Maximian, nicknamed Herculius, was Roman emperor from 286 to 305. He was Caesar from 285 to 286, then Augustus from 286 to 305. He shared the latter title with his co-emperor and superior, Diocletian, whose political brain complemented Maximian's military brawn. Maximian established his residence at Trier but spent most of his time on campaign. In late 285, he suppressed rebels in Gaul known as the Bagaudae. From 285 to 288, he fought against Germanic tribes along the Rhine frontier. Together with Diocletian, he launched a scorched earth campaign deep into Alamannic territory in 288, refortifying the frontier.

Galerius Valerius Maximianus was Roman emperor from 305 to 311. During his reign he campaigned, aided by Diocletian, against the Sasanian Empire, sacking their capital Ctesiphon in 299. He also campaigned across the Danube against the Carpi, defeating them in 297 and 300. Although he was a staunch opponent of Christianity, Galerius ended the Diocletianic Persecution when he issued an Edict of Toleration in Serdica in 311.

Flavius Valerius Constantius "Chlorus", also called Constantius I, was Roman emperor from 305 to 306. He was one of the four original members of the Tetrarchy established by Diocletian, first serving as caesar from 293 to 305 and then ruling as augustus until his death. Constantius was also father of Constantine the Great, the first Christian emperor of Rome. The nickname Chlorus was first popularized by Byzantine-era historians and not used during the emperor's lifetime. After his re-conquering of Roman Britain, he was given the title 'Redditor Lucis Aeternae', meaning 'The Restorer of Eternal Light'.

Marcus Aurelius Valerius Maxentius was a Roman emperor, who reigned from 306 until his death in 312. Despite ruling in Italy and North Africa, and having the recognition of the Senate in Rome, he was not recognized as a legitimate emperor by his fellow emperors.

Constantine I, also known as Constantine the Great, was Roman emperor from AD 306 to 337, the first one to convert to Christianity. Born in Naissus, Dacia Mediterranea, he was the son of Flavius Constantius, a Roman army officer of Illyrian origin who had been one of the four rulers of the Tetrarchy. His mother, Helena, was a Greek Christian of low birth. Later canonized as a saint, she is traditionally attributed with the conversion of her son. Constantine served with distinction under the Roman emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces before being recalled in the west to fight alongside his father in Britain. After his father's death in 306, Constantine became emperor. He was acclaimed by his army at Eboracum, and eventually emerged victorious in the civil wars against emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.

Flavius Valerius Severus, also called Severus II, was a Roman emperor from 306 to 307. After failing to besiege Rome, he fled to Ravenna. It is thought that he was killed there or executed near Rome.

Valerius Licinianus Licinius was Roman emperor from 308 to 324. For most of his reign he was the colleague and rival of Constantine I, with whom he co-authored the Edict of Milan, AD 313, that granted official toleration to Christians in the Roman Empire. He was finally defeated at the Battle of Chrysopolis, and was later executed on the orders of Constantine I.

Galerius Valerius Maximinus, born as Daza, was Roman emperor from 310 to 313. He became embroiled in the Civil wars of the Tetrarchy between rival claimants for control of the empire, in which he was defeated by Licinius. A committed pagan, he engaged in one of the last persecutions of Christians, before issuing an edict of tolerance near his death.

Diocletian, nicknamed "Jovius", was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. Diocles rose through the ranks of the military early in his career, eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name Diocletianus. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Eutropia, a woman of Syrian origin, was the wife of Emperor Maximian.

Galerius Valerius Maximianus was Roman emperor from 305 to 311. During his reign he campaigned, aided by Diocletian, against the Sasanian Empire, sacking their capital Ctesiphon in 299. He also campaigned across the Danube against the Carpi, defeating them in 297 and 300. Although he was a staunch opponent of Christianity, Galerius ended the Diocletianic Persecution when he issued an Edict of Toleration in Serdica in 311.

Galeria Valeria was the daughter of Roman Emperor Diocletian and wife of his co-emperor Galerius.

Flavius Valerius Constantius "Chlorus", also called Constantius I, was Roman emperor from 305 to 306. He was one of the four original members of the Tetrarchy established by Diocletian, first serving as caesar from 293 to 305 and then ruling as augustus until his death. Constantius was also father of Constantine the Great, the first Christian emperor of Rome. The nickname Chlorus was first popularized by Byzantine-era historians and not used during the emperor's lifetime. After his re-conquering of Roman Britain, he was given the title 'Redditor Lucis Aeternae', meaning 'The Restorer of Eternal Light'.

Flavia Maximiana Theodora was a Roman empress, wife of Constantius Chlorus.

Flavia Maxima Fausta Augusta was a Roman empress. She was the daughter of Maximian and second wife of Constantine the Great, who had her executed and excluded from all official accounts for unknown reasons. Historians Zosimus and Zonaras reported that she was executed for adultery with her stepson, Crispus.

Constantine I, also known as Constantine the Great, was Roman emperor from AD 306 to 337, the first one to convert to Christianity. Born in Naissus, Dacia Mediterranea, he was the son of Flavius Constantius, a Roman army officer of Illyrian origin who had been one of the four rulers of the Tetrarchy. His mother, Helena, was a Greek Christian of low birth. Later canonized as a saint, she is traditionally attributed with the conversion of her son. Constantine served with distinction under the Roman emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces before being recalled in the west to fight alongside his father in Britain. After his father's death in 306, Constantine became emperor. He was acclaimed by his army at Eboracum, and eventually emerged victorious in the civil wars against emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.

Flavia Julia Constantia was the daughter of the Roman Emperor Constantius Chlorus and his second wife, Flavia Maximiana Theodora.

Valerius Licinianus Licinius was Roman emperor from 308 to 324. For most of his reign he was the colleague and rival of Constantine I, with whom he co-authored the Edict of Milan, AD 313, that granted official toleration to Christians in the Roman Empire. He was finally defeated at the Battle of Chrysopolis, and was later executed on the orders of Constantine I.

The Western Roman Empire comprised the western provinces of the Roman Empire at any time during which they were administered by a separate independent Imperial court; in particular, this term is used in historiography to describe the period from 395 to 476, where there were separate coequal courts dividing the governance of the empire in the Western and the Eastern provinces, with a distinct imperial succession in the separate courts. The terms Western Roman Empire and Eastern Roman Empire were coined in modern times to describe political entities that were de facto independent; contemporary Romans did not consider the Empire to have been split into two empires but viewed it as a single polity governed by two imperial courts as an administrative expediency. The Western Roman Empire collapsed in 476, and the Western imperial court in Ravenna was formally dissolved by Justinian in 554. The Eastern imperial court survived until 1453.

Maximian, nicknamed Herculius, was Roman emperor from 286 to 305. He was Caesar from 285 to 286, then Augustus from 286 to 305. He shared the latter title with his co-emperor and superior, Diocletian, whose political brain complemented Maximian's military brawn. Maximian established his residence at Trier but spent most of his time on campaign. In late 285, he suppressed rebels in Gaul known as the Bagaudae. From 285 to 288, he fought against Germanic tribes along the Rhine frontier. Together with Diocletian, he launched a scorched earth campaign deep into Alamannic territory in 288, refortifying the frontier.

Diocletian, nicknamed "Jovius", was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. Diocles rose through the ranks of the military early in his career, eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name Diocletianus. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Marcus Aurelius Mausaeus Carausius was a military commander of the Roman Empire in the 3rd century. He was a Menapian from Belgic Gaul, who usurped power in 286, during the Carausian Revolt, declaring himself emperor in Britain and northern Gaul. He did this only 13 years after the Gallic Empire of the Batavian Postumus was ended in 273. He held power for seven years, fashioning the name "Emperor of the North" for himself, before being assassinated by his finance minister Allectus.

Roman Britain was the period in classical antiquity when large parts of the island of Great Britain were under occupation by the Roman Empire. The occupation lasted from AD 43 to AD 410. During that time, the territory conquered was raised to the status of a Roman province.

Flavius Valerius Constantius "Chlorus", also called Constantius I, was Roman emperor from 305 to 306. He was one of the four original members of the Tetrarchy established by Diocletian, first serving as caesar from 293 to 305 and then ruling as augustus until his death. Constantius was also father of Constantine the Great, the first Christian emperor of Rome. The nickname Chlorus was first popularized by Byzantine-era historians and not used during the emperor's lifetime. After his re-conquering of Roman Britain, he was given the title 'Redditor Lucis Aeternae', meaning 'The Restorer of Eternal Light'.

Galerius Valerius Maximianus was Roman emperor from 305 to 311. During his reign he campaigned, aided by Diocletian, against the Sasanian Empire, sacking their capital Ctesiphon in 299. He also campaigned across the Danube against the Carpi, defeating them in 297 and 300. Although he was a staunch opponent of Christianity, Galerius ended the Diocletianic Persecution when he issued an Edict of Toleration in Serdica in 311.

Egypt was a subdivision of the Roman Empire from Rome's invasion of the Ptolemaic Egyptian Kingdom after the battle of Alexandria in 30 BC to its loss by the Byzantine Empire to the Islamic conquests in AD 641. The province encompassed most of modern-day Egypt except for the Sinai, and was bordered by the provinces of Crete and Cyrenaica to the west and Judea, later Arabia Petraea, to the East. Egypt came to serve as a major producer of grain for the empire and had a highly developed urban economy. Aegyptus was by far the wealthiest Eastern Roman province, and by far the wealthiest Roman province outside of Italy. The population of Roman Egypt is unknown, although estimates vary from 4 to 8 million. Alexandria, its capital, was the largest port and second largest city of the Roman Empire.

Allectus was a Roman-Britannic usurper-emperor in Britain and northern Gaul from 293 to 296.

The Western Roman Empire comprised the western provinces of the Roman Empire at any time during which they were administered by a separate independent Imperial court; in particular, this term is used in historiography to describe the period from 395 to 476, where there were separate coequal courts dividing the governance of the empire in the Western and the Eastern provinces, with a distinct imperial succession in the separate courts. The terms Western Roman Empire and Eastern Roman Empire were coined in modern times to describe political entities that were de facto independent; contemporary Romans did not consider the Empire to have been split into two empires but viewed it as a single polity governed by two imperial courts as an administrative expediency. The Western Roman Empire collapsed in 476, and the Western imperial court in Ravenna was formally dissolved by Justinian in 554. The Eastern imperial court survived until 1453.

The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinople. It survived the fragmentation and fall of the Western Roman Empire in the 5th century AD and continued to exist for an additional thousand years until the fall of Constantinople to the Ottoman Empire in 1453. During most of its existence, the empire remained the most powerful economic, cultural, and military force in Europe. The terms "Byzantine Empire" and "Eastern Roman Empire" were coined after the end of the realm; its citizens continued to refer to their empire as the Roman Empire, and to themselves as Romans—a term which Greeks continued to use for themselves into Ottoman times. Although the Roman state continued and its traditions were maintained, modern historians prefer to differentiate the Byzantine Empire from Ancient Rome as it was centred on Constantinople instead of Rome, oriented towards Greek rather than Latin culture, and characterised by Eastern Orthodox Christianity.

Caesar is a title of imperial character. It derives from the cognomen of Julius Caesar, a Roman dictator. The change from being a familial name to a title adopted by the Roman emperors can be traced to AD 68, following the fall of the Julio–Claudian dynasty.

Augustus was an ancient Roman title given as both name and title to Gaius Julius Caesar Octavianus, Rome's first Emperor. On his death, it became an official title of his successor, and was so used by Roman emperors thereafter. The feminine form Augusta was used for Roman empresses and other female members of the Imperial family. The masculine and feminine forms originated in the time of the Roman Republic, in connection with things considered divine or sacred in traditional Roman religion. Their use as titles for major and minor Roman deities of the Empire associated the Imperial system and Imperial family with traditional Roman virtues and the divine will, and may be considered a feature of the Roman Imperial cult.

Marcus Aurelius Mausaeus Carausius was a military commander of the Roman Empire in the 3rd century. He was a Menapian from Belgic Gaul, who usurped power in 286, during the Carausian Revolt, declaring himself emperor in Britain and northern Gaul. He did this only 13 years after the Gallic Empire of the Batavian Postumus was ended in 273. He held power for seven years, fashioning the name "Emperor of the North" for himself, before being assassinated by his finance minister Allectus.

Diocletian, nicknamed "Jovius", was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. Diocles rose through the ranks of the military early in his career, eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name Diocletianus. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.

Maximian, nicknamed Herculius, was Roman emperor from 286 to 305. He was Caesar from 285 to 286, then Augustus from 286 to 305. He shared the latter title with his co-emperor and superior, Diocletian, whose political brain complemented Maximian's military brawn. Maximian established his residence at Trier but spent most of his time on campaign. In late 285, he suppressed rebels in Gaul known as the Bagaudae. From 285 to 288, he fought against Germanic tribes along the Rhine frontier. Together with Diocletian, he launched a scorched earth campaign deep into Alamannic territory in 288, refortifying the frontier.

Allectus was a Roman-Britannic usurper-emperor in Britain and northern Gaul from 293 to 296.

Flavius Valerius Constantius "Chlorus", also called Constantius I, was Roman emperor from 305 to 306. He was one of the four original members of the Tetrarchy established by Diocletian, first serving as caesar from 293 to 305 and then ruling as augustus until his death. Constantius was also father of Constantine the Great, the first Christian emperor of Rome. The nickname Chlorus was first popularized by Byzantine-era historians and not used during the emperor's lifetime. After his re-conquering of Roman Britain, he was given the title 'Redditor Lucis Aeternae', meaning 'The Restorer of Eternal Light'.

Galerius Valerius Maximianus was Roman emperor from 305 to 311. During his reign he campaigned, aided by Diocletian, against the Sasanian Empire, sacking their capital Ctesiphon in 299. He also campaigned across the Danube against the Carpi, defeating them in 297 and 300. Although he was a staunch opponent of Christianity, Galerius ended the Diocletianic Persecution when he issued an Edict of Toleration in Serdica in 311.

Lucius Domitius Domitianus or, rarely, Domitian III, was a Roman usurper against Diocletian, who seized power for a short time in Egypt.

In the Late Roman Empire, usually dated 284 AD to 602 AD, the regional governance district known as the Roman or civil diocese was made up of a grouping of provinces each headed by a Vicarius, who were the representatives of praetorian prefects. There were initially twelve dioceses, rising to fourteen by the end of the 4th century.

Magister militum was a top-level military command used in the later Roman Empire, dating from the reign of Constantine the Great. The term referred to the senior military officer of the empire. In Greek sources, the term is translated either as strategos or as stratelates.

Theodosius I, also called Theodosius the Great, was Roman emperor from 379 to 395. During his reign, he succeeded in a crucial war against the Goths, as well as in two civil wars, and was instrumental in establishing the creed of Nicaea as the orthodox doctrine for Christianity. Theodosius was the last emperor to rule the entire Roman Empire before its administration was permanently split between two separate courts.

The fall of the Western Roman Empire was the loss of central political control in the Western Roman Empire, a process in which the Empire failed to enforce its rule, and its vast territory was divided into several successor polities. The Roman Empire lost the strengths that had allowed it to exercise effective control over its Western provinces; modern historians posit factors including the effectiveness and numbers of the army, the health and numbers of the Roman population, the strength of the economy, the competence of the emperors, the internal struggles for power, the religious changes of the period, and the efficiency of the civil administration. Increasing pressure from invading barbarians outside Roman culture also contributed greatly to the collapse. Climatic changes and both endemic and epidemic disease drove many of these immediate factors. The reasons for the collapse are major subjects of the historiography of the ancient world and they inform much modern discourse on state failure.

Thessaly is a traditional geographic and modern administrative region of Greece, comprising most of the ancient region of the same name. Before the Greek Dark Ages, Thessaly was known as Aeolia, and appears thus in Homer's Odyssey.

Galatia was an ancient area in the highlands of central Anatolia, roughly corresponding to the provinces of Ankara and Eskişehir, in modern Turkey. Galatia was named after the Gauls from Thrace, who settled here and became a small transient foreign tribe in the 3rd century BC, following the Gallic invasion of the Balkans in 279 BC. It has been called the "Gallia" of the East.

Lycaonia was a large region in the interior of Asia Minor, north of the Taurus Mountains. It was bounded on the east by Cappadocia, on the north by Galatia, on the west by Phrygia and Pisidia, while to the south it extended to the chain of Mount Taurus, where it bordered on the country popularly called in earlier times Cilicia and in the Byzantine period Isauria; but its boundaries varied greatly at different times. The name is not found in Herodotus, but Lycaonia is mentioned by Xenophon as traversed by Cyrus the Younger on his march through Asia. That author describes Iconium as the last city of Phrygia; and in Acts 14:6 Paul, after leaving Iconium, crossed the frontier and came to Lystra in Lycaonia. Ptolemy, on the other hand, includes Lycaonia as a part of the province of Cappadocia, with which it was associated by the Romans for administrative purposes; but the two countries are clearly distinguished both by Strabo and Xenophon and by authorities generally.

The Cantiaci or Cantii were an Iron Age Celtic people living in Britain before the Roman conquest, and gave their name to a civitas of Roman Britain. They lived in the area now called Kent, in south-eastern England. Their capital was Durovernum Cantiacorum, now Canterbury.

Judea or Judaea is a mountainous region in the southern part of the modern States of Palestine and Israel.

The Lion, the Witch and the Wardrobe is a fantasy novel for children by C. S. Lewis, published by Geoffrey Bles in 1950. It is the first published and best known of seven novels in The Chronicles of Narnia (1950–1956). Among all the author's books, it is also the most widely held in libraries. Although it was originally the first of The Chronicles of Narnia, it is volume two in recent editions that are sequenced by the stories' chronology. Like the other Chronicles, it was illustrated by Pauline Baynes, and her work has been retained in many later editions.

Narnia is a fantasy world created by C. S. Lewis as the primary location for his series of seven fantasy novels for children, The Chronicles of Narnia. The world is named after the country of Narnia, where much of the Chronicles takes place.