Marcian was born in AD 392 and most likely Illyrian by birth. His father had been a soldier and Marcian too enrolled as a soldier in the city of Philippopolis in Thrace. He served in AD 421 as a tribune against the Persians, but due to illness, never took part in the fighting. After this he served for fifteen years as a personal assistant (domesticus) to the commander Ardaburius and his son Aspar. This service took him under the command of Aspar to Africa (AD 431 - AD 433) , where he allegedly was even a captive of the Vandals for some time before being released again. After his release, not much is known about Marcian until his accension to the throne. At Constantinople Marcian became a senator and was a well-known and popular person. He was about sixty years old when Theodosius II died (450).
With the death of Theodosius II under somewhat mysterious circumstances, and no heirs of his own, power over the eastern empire should have fallen to the western emperor Valentinian III. Valentinian was married to Licinia Eudoxia, the only surviving child of Theodosius II, leaving it in his power to decide if he wanted to rule alone or appoint another eastern emperor. Pulcheria, Theodosius II's sister, agreed to marry Marcian, who was a widower, in order to thereby formally connect him with the dynasty of the House of Valentinian.
With the support of the last representative of the Theodosian house in the east and the head general, Marcian received the support of the Senate and the armies. On August 25, 450, Pulcheria gave him the imperial diadem, a unique event implying that an Augusta shared in the imperial power. Valentinian III in the west though at first refused to recognize the accession of the eastern throne by Marcian, but later accepted the decision. Marcian did remain largely beholden to Aspar, however. Perhaps because of his support, Marcian made the general a patrician. The emperor also appointed his son, Ardabur, the commander-in-chief for the East (magister utriusque militiae per Orientem).
One of his first acts as emperor was to order Chrysaphius Zstommas to be put to death. He was a very unpopular advisor to Theodosius II and an enemy of Pulcheria. Marcian immediately began to change the policy towards Atitila and the Huns. 'I have iron for Attila, but no gold.' During the late stages of Theodosius II reign and with the help of Chrysaphius, huge subsidies had to be paid to Attila the Hun, for safekeeping.
Marcian's decision was conceived with suspicion by his own people fearing invasion from Attila, but it turned out to be enormously successful. The aristocracy, which had been opposed to the treaty with the barbarians, supported this action. Even more important was that the Hun Empire became so absorbed in western imperial politics that they paid litle attention to the rebellious Marcian. Attila died soon after Marcian's decision and his empire disintegrated, ending the threat from the Huns. Marcian formed alliances with many peoples previously under Hunnic domination, especially the Ostrogoths. He permitted those peoples to settle as federates in Pannonia, Thrace and Illyricum. Marcian's policy resulted in saving the imperial treasury enormous sums.
In AD 451 the Ecumenical Council of the Church at Chalcedon was held, which was to define the beliefs which is still the basis of religious teaching for the Eastern Orthodox Church today. The council at Chalcedon was important because it more clearly outlined the increasing split between east and west. This council was a defining moment for the separation of the two halves of Christendom.
Marcian's reign, unlike the west, was largely free from any military or political crisis. The only noteworthy events were a revolt by monks in Palestine in 453 AD, and a similar occurence in Alexandria. On both occasion Marcian sent troops to quickly surpress the uprising. There were some campaigns against Saracens in Syria and against the Blemmyes in Egypt. The lack of any long-term, large-scale wars meant that the emperor was able to amass huge funds. Marician was trying to avoid confrontation throughout his reign. So it came to no surprise that the assasination of the western Emperor Valentinian III, and the sack of Rome by the Vandals in AD 455 was met with silence from the east. The only action he took was to request the return of the empress Eudoxia and her daughters.
Apart from a lack of military spirit, Marcian proved to be a very able administrator, and many reforms introduced by Marcian, in addition to the halting of payments to the Huns, made the financial situation of Constantinople a very strong one. He left his successor one hundred thousand pounds of gold.
Early in AD 457 Marcian fell ill and died after a five month illness. He was sincerely mourned by the people of Constantinople who saw his reign as a golden age.