Venice didn’t appear out of nothing – there was something before which led to the Venice we know as the Serenissima.
Domenicus Monegarius was the sixth doge of Venice, from 765, following the deposition and blinding of duke Galla, and was blinded and deposed in 764.
Galla, the fifth doge of Venice, only ruled for one year, which was marked by violence.
Deusdedit was the fourth doge of Venice, ruling from 742 to 755, but we know little more about him than of the previous doges and the “magistri militum”.
The earliest written source related to the inhabitants of the Venetian lagoons, is a letter from Cassiodorus, written in 537.
Venetia existed within the Exarchate of Ravenna, as part of the Byzantine Empire, and what happened in the Exarchate mattered to Venetia.