Disappearance of the military triumph

[Theodosius the Great]

The I would like to ask is when did church ceremony replace, or become more 'fashionable' for an emperor to mark his victories? For example Heraklius had a message read out in the Hagio Sophia to announce his victories over Khusro II and Maurice held a ceremony in the same church. When did this begin to happen, and any theories on why?

For the East my guess is when the Patriarchs began crowning emperors with Marcian.

Why did this start with Marcian? The simple answer is that he needed all the legitimacy he could get since he was an outsider, not being from the Theodosian House into which he married. Since the act was apparently effacacious in warding off revolts Marcian's successors made it into a practice.

The high civil and military officials took part in the enthronement of a new monarch, often by means of a palace or military revolution. Legally, the people participated in the government only through the Church. From the time of Marcianus, the Byzantine emperors were crowned by the Patriarchs of Constantinople. -source: Catholic Encyclopedia

So, I suppose I agree with Lyceum to an extent. Church ceremonies became more potent in confering legitimacy due to their solemnity rather than triumphal celebrations which degenerated into public revelry and debauchery.

~Theo