Marcian was born in AD 392, the son of a Thracian or Illyrian soldier.
After this he served for fifteen years as a commander under Ardaburius and his son Aspar.
With the death of Theodosius II, who had no heirs of his own, power over the eastern empire should have fallen to the western emperor Valentinian III, leaving it for him to decide if he wanted to rule alone or appoint another eastern emperor. However, relations between east and west were not that good and both the court and the people of Constantinople would have objected to being ruled by a western emperor.
Theodosius II himself was also known to have been opposed to this and on his death bed, he is to have said to Marcian who was present alongside Aspar (Aspar was 'Master of Soldiers', but an Arian Christian and hence not a suitable candidate for the throne),
Theodosius II's will was obeyed and Marcian did succeed him as emperor in AD 450.
Marcian's first act as emperor was to order Chrysaphius Zstommas to be put to death. He was a deeply unpopular advisor to Theodosius II and an enemy of Pulcheria.
In AD 451 the Ecumenical Council of the Church at Chalcedon was held, which was to define the creed which is still the basis of religious teaching for the Eastern Orthodox Church today.
Pulcheria died in 453, leaving her few belongings to the poor.
Marcian's reign was largely free from any military or political crisis, such which befell the west.
But apart from such criticism, Marcian proved a very able administrator. Not least because of the cancellation of tribute payments to the Huns, but so too, due to many reforms introduced by Marcian did the financial situation of Constantinople was much improved.
Early in AD 457 Marcian fell ill and after a five month illness he died. He was sincerely mourned by the people of Constantinople who saw his reign as a golden age.