Heraclius in the context of "Issus (town)"

The Arab conquest of Egypt, led by the army of Amr ibn al-As, under the Rashidun Caliphate took place between 639 and 642 AD. It ended the Roman period in Egypt which began in 30 BC and lasted for seven centuries, and more broadly, the Greco-Roman period which lasted for about a millennium.

Prior to the conquest, Byzantine rule in the country had been shaken, as Egypt had been conquered and occupied by the Sasanian Empire for a decade between 618–629, before being reconquered by the Byzantines under emperor Heraclius. The Caliphate took advantage of Byzantines' exhaustion to invade Egypt.

The praetorian prefecture (Latin: praefectura praetorio; in Greek variously named ἐπαρχότης τῶν πραιτωρίων or ὑπαρχία τῶν πραιτωρίων) was the largest administrative division of the late Roman Empire, above the mid-level dioceses and the low-level provinces. Praetorian prefectures originated in the reign of Constantine I (r. 306–337), reaching their more or less final form in the last third of the 4th century and surviving until the 7th century, when the reforms of Heraclius diminished the prefecture's power, and the Muslim conquests forced the Eastern Roman Empire to adopt the new theme system. Elements of the prefecture's administrative apparatus, however, are documented to have survived in the Byzantine Empire until the first half of the 9th century.

Byzantine Anatolia refers to the peninsula of Anatolia (located in present-day Turkey) during the rule of the Byzantine Empire. Anatolia was of vital importance to the empire following the Muslim invasion of Syria and Egypt during the reign of the Byzantine Emperor Heraclius in the years 634–645 AD. Over the next two hundred and fifty years, the region suffered constant raids by Arab Muslim forces raiding mainly from the cities of Antioch, Tarsus, and Aleppo near the Anatolian borders. However, the Byzantine Empire maintained control over the Anatolian peninsula until the High Middle Ages (years 1080s), when imperial authority in the area began to collapse.

The Byzantine Empire re-established control over parts of Anatolia during the First Crusade, and following the sack of Constantinople during the Fourth Crusade, Anatolia became the heartland of the successor states of the Empire of Nicaea and Empire of Trebizond. Following the retaking of Constantinople in 1261, the region gradually passed out of Byzantine control and into the hands of the Ottoman Turks as the empire gradually crumbled. The last Byzantine fortress of Philadelphia fell in 1399, and the last Byzantine presence in the area at Trapezus ended in 1461 with the fall of Trebizond.

The Byzantine Empire's history is generally periodised from late antiquity until the Fall of Constantinople in 1453 AD. From the 3rd to 6th centuries, the Greek East and Latin West of the Roman Empire gradually diverged, marked by Diocletian's (r. 284–305) formal partition of its administration in 285, the establishment of an eastern capital in Constantinople by Constantine I in 330, and the adoption of Christianity as the state religion under Theodosius I (r. 379–395), with others such as Roman polytheism being proscribed. Although the Western half of the Roman Empire had collapsed in 476, the Eastern half remained stable and emerged as one of the most powerful states in Europe, a title it held for most of its existence. Under the reign of Heraclius (r. 610–641), the Empire's military and administration were restructured and adopted Greek for official use instead of Latin. While there was an unbroken continuity in administration and other features of Roman society, historians have often distinguished the Byzantine epoch from earlier eras in Roman history for reasons including the imperial seat moving from Rome to Constantinople and the predominance of Greek instead of Latin.

The borders of the Empire evolved significantly over its existence, as it went through several cycles of decline and recovery. During the reign of Justinian I (r. 527–565), the Empire reached its greatest extent after reconquering much of the historically Roman western Mediterranean coast, including north Africa, Italy, and Rome itself, which it held for two more centuries. During the reign of Maurice (r. 582–602), the Empire's eastern frontier was expanded and the north stabilised. However, his assassination caused a two-decade-long war with Sassanid Persia which exhausted the Empire's resources and contributed to major territorial losses during the Muslim conquests of the 7th century. In a matter of years the Empire lost its richest provinces, Egypt and Syria, to the Arabs.

The Estoire d'Eracles ("History of Heraclius") is an anonymous Old French translation and continuation of the Latin History of Deeds Done Beyond the Sea by William of Tyre. It begins with recapture of Jerusalem by the Roman emperor Heraclius in AD 630, from which it takes its name, and continues down to 1184. The continuation recounts the history of the Crusader states from Saladin's capture of Jerusalem in 1187 down to 1277.

The translation was made between 1205 and 1234, possibly in Western Europe. Several times the text of the translation was changed and the manuscripts preserve different versions of William's text. The continuations were added to the translation between 1220 and 1277. There are two different versions of the first continuation, covering the years 1185–1225. Both reflect the political attitudes of the Crusader aristocracy. There are 49 surviving manuscripts of the Eracles. Of these, 44 contain a first continuation drawn from the Chronicle of Ernoul and five (the so-called Colbert–Fontainebleau manuscripts) contain a different version. Twelve of the manuscripts contain a unique continuation for the years 1229–1261 drawn from the independent work known as the Rothelin Continuation.

The praetorian prefect (Latin: praefectus praetorio; Greek: ἔπαρχος/ὕπαρχος τῶν πραιτωρίων) was a high office in the Roman Empire established by Emperor Augustus in 2 BC. Originating as the commander of the Praetorian Guard, the office gradually acquired extensive legal and administrative functions, with its holders becoming the Emperor's chief aides. Under Constantine I, the office was much reduced in power and transformed into a purely civilian administrative post, while under his successors, territorially defined praetorian prefectures emerged as the highest-level administrative division of the Empire. The prefects again functioned as the chief ministers of the state, with many laws addressed to them by name. In this role, praetorian prefects continued to be appointed by the Eastern Roman Empire (and the Ostrogothic Kingdom) until the reign of Heraclius in the 7th century AD, when wide-ranging reforms reduced their power and converted them to mere overseers of provincial administration. The last traces of the prefecture disappeared in the Byzantine Empire by the 840s.

The term praefectus praetorio was often abbreviated in inscriptions as "PR PR" or "PPO".

Phocas (Latin: Focas; Ancient Greek: Φωκάς, romanized: Phōkás; 547 – 5 October 610) was Eastern Roman emperor from 602 to 610. Initially a middle-ranking officer in the Roman army, Phocas rose to prominence as a spokesman for dissatisfied soldiers in their disputes with the court of the Emperor Maurice. When the army rebelled in 602, Phocas emerged as the leader of the mutiny. The revolt led to the overthrow and execution of Maurice in November 602.

Phocas deeply mistrusted the uncooperative elite of Constantinople, to whom he was a usurper and a provincial boor. He therefore attempted to base his regime on relatives installed in high military and administrative positions. He immediately faced challenges in domestic and foreign affairs, and responded with little success. He dealt with domestic opposition with increasing ruthlessness that alienated ever wider circles, including some of his own household. The Sasanian Empire launched a massive invasion of the eastern provinces. Finally, the exarch of Africa, Heraclius the Elder, rebelled against Phocas and gained wide support throughout the empire. Phocas attempted to use border troops to crush the rebellion, but this only resulted in allowing invaders to break into the heartlands of the Empire. Heraclius the Elder's son, Heraclius, took Constantinople on 5 October 610, executed Phocas the same day, and declared himself emperor.

The siege of Constantinople in 626 by the Sassanid Persians and Avars, aided by large numbers of allied Slavs, ended in a strategic victory for the Byzantines. The failure of the siege saved the empire from collapse, and, combined with other victories achieved by Emperor Heraclius (r. 610–641) the previous year and in 627, enabled Byzantium to regain its territories and end the destructive Roman–Persian Wars by enforcing a treaty with borders status quo c. 590.