Arcadius in the context of "West Roman Empire"

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.

Honorius (/hoʊˈnɔːriəs/; 9 September 384 – 15 August 423) was Roman emperor from 393 to 423. He was the younger son of emperor Theodosius I and his first wife Aelia Flaccilla. After the death of Theodosius in 395, Honorius, under the regency of Stilicho, ruled the western half of the empire while his brother Arcadius ruled the eastern half. His reign over the Western Roman Empire was notably precarious and chaotic. In 410, Rome was sacked for the first time since the Battle of the Allia almost 800 years prior.

Theodosius II (Ancient Greek: Θεοδόσιος Theodosios; 10 April 401 – 28 July 450), called "the Calligrapher", was Roman emperor from 402 to 450. He was proclaimed Augustus as an infant and ruled as the Eastern Empire's sole emperor after the death of his father Arcadius in 408. His reign was marked by the promulgation of the Theodosian law code and the construction of the Theodosian walls of Constantinople. He also presided over the outbreak of two great Christological controversies, Nestorianism and Eutychianism.

Gainas (?-400 AD, Greek: Γαϊνάς) was a Gothic leader who served the Eastern Roman Empire as magister militum during the reigns of Theodosius I and Arcadius. He played an important role in the events in the eastern part of the empire by the end of the 4th century.

Aelia Flavia Flaccilla (died 386), better known simply as Aelia Flacilla or Flacilla, was a Roman empress and first wife of the Roman Emperor Theodosius I. She was of Hispanian Roman descent. During her marriage to Theodosius, she gave birth to two sons – future Emperors Arcadius and Honorius – and a daughter, Aelia Pulcheria.

Aelia Eudoxia (/ˈiːliə juˈdɒkʃə -ˈdɒksiə/; Ancient Greek: Αἰλία Εὐδοξία; died 6 October 404) was Eastern Roman empress by marriage to the Roman emperor Arcadius. The marriage was arranged by Eutropius, one of the eunuch court officials, who was attempting to expand his influence. As Empress, she came into conflict with John Chrysostom, the Patriarch of Constantinople, who denounced imperial and clerical excess. She had five children, four of whom survived to adulthood, including her only son and future emperor Theodosius II, but she had two additional pregnancies that ended in either miscarriages or stillbirths and she died as a result of the latter one.