Diocletian in the context of "Carinus"

In modern historiography, the Western Roman Empire were the Roman Empire's western provinces, collectively, during any period in which they were administered separately from the eastern provinces by a separate, independent imperial court. Particularly during the period from AD 395 to 476, there were separate, coequal courts dividing the governance of the empire into the Western provinces 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 for administrative expediency. The Western Empire collapsed in 476, and the Western imperial court in Ravenna disappeared by 554, at the end of Justinian's Gothic War.

Though there were periods with more than one emperor ruling jointly before, the view that it was impossible for a single emperor to govern the entire Empire was institutionalized by emperor Diocletian following the disastrous civil wars and disintegrations of the Crisis of the Third Century. He introduced the system of the Tetrarchy in 286, with two senior emperors titled Augustus, one in the East and one in the West, each with an appointed subordinate and heir titled Caesar. Though the tetrarchic system would collapse in a matter of years, the East–West administrative division would endure in one form or another over the coming centuries. As such, the unofficial Western Roman Empire would exist intermittently in several periods between the 3rd and 5th centuries. Some emperors, such as Constantine I and Theodosius I, governed, if briefly, as the sole Augustus across the Roman Empire. On the death of Theodosius in 395, the empire was divided between his two infant sons, with Honorius as his successor in the West governing briefly from Mediolanum then from Ravenna, and Arcadius as his successor in the East governing from Constantinople.

The Roman provinces (Latin: provincia, pl. provinciae) were the administrative regions of Ancient Rome outside Roman Italy that were controlled by the Romans under the Roman Republic and later the Roman Empire. Each province was ruled by a Roman appointed as governor.

For centuries, it was the largest administrative unit of the foreign possessions of ancient Rome. With the administrative reform initiated by Diocletian, it became a third level administrative subdivision of the Roman Empire, or rather a subdivision of the imperial dioceses (in turn subdivisions of the imperial prefectures).

Shkodër (/ˈʃkoʊdər/ SHKOH-dər, Albanian: [ˈʃkɔdəɾ]; Albanian definite form: Shkodra; historically known as Scodra or Scutari) is the fifth-most-populous city of Albania and the seat of Shkodër County and Shkodër Municipality. Shkodër has been continuously inhabited since the Early Bronze Age (c. 2250–2000 BC), and has roughly 2,200 years of recorded history. The city sprawls across the Plain of Mbishkodra between the southern part of Lake Shkodër and the foothills of the Albanian Alps on the banks of the Buna, Drin and Kir rivers. Due to its proximity to the Adriatic Sea, Shkodër is affected by a seasonal Mediterranean climate with continental influences.

An urban settlement called Skodra was founded by the Illyrian tribe of Labeatae in the 4th century BCE. It became the capital of the Illyrian kingdom under the Ardiaei and Labeatae and was one of the most important cities of the Balkans in ancient times. It has historically developed on a 130 m (430 ft) hill strategically located in the outflow of Lake Shkodër into the Buna. The Romans annexed the city after the third Illyrian War in 168 BC, when the Illyrian king Gentius was defeated by the Roman force of Anicius Gallus. In the 3rd century AD, Shkodër became the capital of Praevalitana, due to the administrative reform of the Roman Emperor Diocletian. With the spread of Christianity in the 4th century AD, the Archdiocese of Scodra was founded and was assumed in 535 by Byzantine Emperor Justinian I.

Augustus (plural Augusti; /ɔːˈɡʌstəs/ aw-GUST-əs, Classical Latin: [au̯ˈɡʊstʊs]; "majestic", "great" or "venerable") was the main title of the Roman emperors during Antiquity. It was given as both name and title to Gaius Julius Caesar Octavianus (often referred to simply as Augustus) in 27 BC, marking his accession as Rome's first emperor. On his death, it became an official title of his successor, and was so used by all 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 family with traditional Roman virtues and the divine will and may be considered a feature of the Roman imperial cult.

In Rome's Greek-speaking provinces, "Augustus" was translated as Sebastos (Σεβαστός), or Hellenised as Augoustos (Αὔγουστος); these titles continued to be used in the Byzantine Empire until the Fall of Constantinople in 1453, although they gradually lost their imperial exclusivity in favour of Basileus and Autokrator.

Constantine I (27 February 272 – 22 May 337), also known as Constantine the Great, or known mononymously as Constantine, was Roman emperor from AD 306 to 337 and the first Roman emperor to convert to Christianity. He played a pivotal role in elevating the status of Christianity in Rome, the Edict of Milan decriminalising Christian practice and ceasing Christian persecution. This was a turning point in the Christianisation of the Roman Empire. He founded the city of Constantinople (now Istanbul) and made it the capital of the Empire, which it remained for over a millennium.

Born in Naissus, a city located in the province of Moesia Superior (now Niš, Serbia), Constantine was the son of Flavius Constantius, a Roman army officer from Moesia Superior, who would become one of the four emperors of the Tetrarchy. His mother, Helena, was a woman of low birth, probably from Bithynia. Later canonised as a saint, she is credited for the conversion of her son in some traditions, though others believe that Constantine converted her. He served with distinction under emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces against the Persians, before being recalled to the west in AD 305 to fight with his father in the province of Britannia. After his father's death in 306, Constantine was proclaimed as augustus (emperor) by his army at Eboracum (York, England). He eventually emerged victorious in Civil wars of the Tetrarchy against the emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.

In modern scholarship, the "late" period of the Roman army begins with the accession of the Emperor Diocletian in AD 284, and ends in 480 with the death of Julius Nepos, being roughly coterminous with the Dominate. During the period 395–476, the army of the Roman Empire's western half progressively disintegrated, while its counterpart in the East, known as the East Roman army (or the early Byzantine army) remained largely intact in size and structure until the reign of Justinian I (r. AD 527–565).

The Imperial Roman army of the Principate (30 BC – 284 AD) underwent a significant transformation as a result of the chaotic 3rd century. Unlike the army of the Principate, the army of the 4th century was heavily dependent on conscription and its soldiers were paid much less than in the 2nd century. Barbarians from outside the empire probably supplied a much larger proportion of the late army's recruits than in the army of the 1st and 2nd centuries, but there is little evidence that this adversely affected the army's combat performance.

The constitution of the late Roman Empire was an unwritten set of guidelines and principles passed down, mainly through precedent, which defined the manner in which the late Roman Empire was governed. As a matter of historical convention, the late Roman Empire emerged from the Roman Principate (the early Roman Empire), with the accession of Diocletian in AD 284, his reign marking the beginning of the Tetrarchy. The constitution of the Dominate outrightly recognized monarchy as the true source of power, and thus ended the facade of dyarchy, in which emperor and Senate governed the empire together.

Diocletian's reforms to the Imperial government finally put an end to the period when the old Republican magistracies (e.g. consuls and praetors) held real powers. From then, the consuls had almost no real duties beyond that of presiding at Senate meetings and the duties of the lesser magistrates were effectively just hosting various games, e.g. chariot racing. Most other lesser magistracies simply disappeared.