Khosrow I in the context of "Emperor Justinian"

Justinian I (Latin: Iustinianus, Ancient Greek: Ἰουστινιανός, romanized: Ioustinianós; 482 – 14 November 565), also known as Justinian the Great, was Roman emperor from 527 to 565.

His reign was marked by the ambitious but only partly realized renovatio imperii, or "restoration of the Empire". This ambition was expressed by the partial recovery of the territories of the defunct Western Roman Empire. His general, Belisarius, swiftly conquered the Vandal Kingdom in North Africa. Subsequently, Belisarius, Narses, and other generals conquered the Ostrogothic Kingdom, restoring Dalmatia, Sicily, Italy, and Rome to the empire after more than half a century of rule by the Ostrogoths. The praetorian prefect Liberius reclaimed the south of the Iberian Peninsula, establishing the province of Spania. These campaigns re-established Roman control over the western Mediterranean, increasing the Empire's annual revenue by over a million solidi. During his reign, Justinian also subdued the Tzani, a people on the east coast of the Black Sea that had never been under Roman rule before. He engaged the Sasanian Empire in the east during Kavad I's reign, and later again during Khosrow I's reign; this second conflict was partially initiated due to his ambitions in the west.

Kavad I (Middle Persian: 𐭪𐭥𐭠𐭲 Kawād; 473 – 13 September 531) was the Sasanian King of Kings of Iran from 488 to 531, including a two or three-year interruption. A son of Peroz I (r. 459–484), he was crowned by the nobles to replace his deposed and unpopular uncle Balash (r. 484–488).

Inheriting a declining empire where the authority and status of the Sasanian kings had largely weakened, Kavad tried to reorganize his empire by introducing many reforms whose implementation was completed by his son and successor, Khosrow I. They were made possible by Kavad's use of the Mazdakite preacher Mazdak, leading to a social revolution that weakened the authority of the nobility and the clergy. Because of this, and the execution of the powerful king-maker Sukhra, Kavad was deposed and imprisoned in the Castle of Oblivion. He was replaced by his brother Jamasp. However, with the aid of his sister and an officer named Siyawush, Kavad and some of his followers fled east to the territory of the Hephthalite king, who provided him with an army. This enabled Kavad to restore himself to the throne in 498/9.

The Sasanian army was the primary military body of the Sasanian armed forces, serving alongside the Sasanian navy. The birth of the army dates back to the rise of Ardashir I (r. 224–241), the founder of the Sasanian Empire, to the throne. Ardashir aimed at the revival of the Persian Empire, and to further this aim, he reformed the military by forming a standing army which was under his personal command and whose officers were separate from satraps, local princes and nobility. He restored the Achaemenid military organizations, retained the Parthian cavalry model, and employed new types of armour and siege warfare techniques. This was the beginning for a military system which served him and his successors for over 400 years, during which the Sasanian Empire was, along with the Roman Empire and later the Eastern Roman Empire, one of the two superpowers of Late Antiquity in Western Eurasia. During the reign of Khosrow the Sasanian army underwent major reforms. The Sasanian army protected Eranshahr ("the realm of Iran") from the East against the incursions of central Asiatic nomads like the Hephthalites and Turks, while in the west it was engaged in a recurrent struggle against the Roman Empire.

Khosrow II (spelled Chosroes II in classical sources; Middle Persian: 𐭧𐭥𐭮𐭫𐭥𐭣𐭩, romanized: Husrō and Khosrau), commonly known as Khosrow Parviz (New Persian: خسرو پرویز, "Khosrow the Victorious"), is considered to be the last great Sasanian King of Kings (Shahanshah) of Iran, ruling from 590 to 628, including an interruption of one year.

Khosrow II was the son of Hormizd IV (reigned 579–590), and the grandson of Khosrow I (reigned 531–579). He was the last king of Iran to have a lengthy reign before the Muslim conquest of Iran, which began five years after his execution. He lost his throne, then regained it with the help of the Byzantine emperor Maurice, and, a decade later, went on to emulate the feats of the Achaemenids, conquering the rich Roman provinces of the Middle East; much of his reign was spent in wars with the Byzantine Empire and struggling against usurpers such as Bahram Chobin and Vistahm.

Shapur II (Middle Persian: 𐭱𐭧𐭯𐭥𐭧𐭥𐭩 Šābuhr, 309–379), also known as Shapur the Great, was the tenth King of Kings (Shahanshah) of the Sasanian Empire. He took the title at birth and held it until his death at age 70, making him the longest-reigning monarch in Iranian history. He was the son of Hormizd II (r. 302–309).

His reign saw the military resurgence of the country and the expansion of its territory, which marked the start of the first Sasanian golden era. Thus, along with Shapur I, Kavad I and Khosrow I, he is regarded as one of the most illustrious Sasanian kings. His three direct successors, on the other hand, were less successful. At the age of 16, he launched enormously successful military campaigns against Arab insurrections and tribes.

The Sasanian Avesta or Great Avesta refers to the anthology of Zoroastrian literature produced during the Sasanian period. They are said to have been written down during the reign of Khosrow. Most of this work is now lost, but its content and structure can be reconstructed from references found in a number of texts from the 9th century onward.

Compared to the extant Avesta, the Sasanian Avesta was much larger and organized into 21 distinct volumes called nasks (Avestan: naska; Middle Persian: nask, 'bundle'). Of those, only one is preserved in its entirety, while others are either lost or only preserved in fragments.

Damascius (/dəˈmæʃəs/; Ancient Greek: Δαμάσκιος; c. 462 – after 538), known as "the last of the Athenian Neoplatonists", was the last scholarch of the neoplatonic Athenian school. He was one of the neoplatonic philosophers who left Athens after laws confirmed by emperor Justinian I forced the closure of the Athenian school in c. 529 AD. After he left Athens, he may have sought refuge in the court of the Persian King Chrosroes, before being allowed back into the Byzantine Empire. His surviving works consist of three commentaries on the works of Plato, and a metaphysical text entitled Difficulties and Solutions of First Principles.

Spāhbad (also spelled spahbod) is a Middle Persian title meaning "army chief" or commander used chiefly in the Sasanian Empire. Originally there was a single spāhbad, called the Ērān-spāhbed, who functioned as the generalissimo of the Sasanian army. From the time of Khosrow I (r. 531–579) on, the office was split in four, with a spāhbad for each of the cardinal directions. After the Muslim conquest of Persia, the spāhbed of the East managed to retain his authority over the inaccessible mountainous region of Tabaristan on the southern shore of the Caspian Sea, where the title, often in its Islamic form ispahbedh (Persian: اسپهبذ; in Arabic: اصبهبذ ʾiṣbahbaḏ), survived as a regnal title until the Mongol conquests of the 13th century. An equivalent title of Persian origin, ispahsālār or sipahsālār, gained great currency across the Muslim world in the 10th–15th centuries.

The title was also adopted by the Armenians (Armenian: սպարապետ, [a]sparapet) and the Georgians (Georgian: სპასპეტი, spaspeti), as well as Khotan (spāta) and the Sogdians (spʾdpt) in Central Asia. It is also attested in Greek sources as aspabedēs (ἀσπαβέδης). The title was revived in the 20th century by the Pahlavi dynasty, in the Modern Persian form sepahbod (سپهبد), equivalent to a three-star Lieutenant General, ranking below arteshbod (full General).