Excerpts from Books and Wikipedia
"Marcian reversed many of the actions of his predecessor, Emperor Theodosius II, in religious matters and the Eastern Roman Empire's relationship with the Huns under Attila. Marcian almost immediately revoked all treaties with Attila, ending all subsidy payments to him. In 452, while Attila was raiding Italy, then a part of the Western Roman Empire, Marcian launched expeditions across the Danube into the Hungarian plain, defeating the Huns in their own heartland. This action, accompanied by the famine and plague that broke out in northern Italy, allowed Marcian to bribe Attila into retreating from the Italian peninsula. After the death of Attila in 453, Marcian took advantage of the resulting fragmentation of the Hunnic confederation, settling numerous tribes within Eastern Roman lands as foederati (subject tribes which gave military service in exchange for various benefits). Marcian also convened the Council of Chalcedon, which reversed the outcome of the previous Second Council of Ephesus, and declared that Jesus had two natures, divine and human. Marcian died on 26 January 457, leaving the Eastern Roman Empire with a treasury surplus of seven million solidi." [Wikipedia]