Venice started as a Byzantine duchy, ruled by a “dux”, but at some point, they started choosing their own dux — or doge. When, or even who, is not clear.
This document is the earliest description of the translation of St Mark to Venice in 827–828, and also of early Venice. This is a translation by René Seindal.
Venice was an independent state for almost a millennium, but it might note have been. It all hinged on a single battle fought in the Venetian lagoon in 810.
In late Antiquity the north-east of the Italian peninsula suffered many invasions. The wars caused people to move to the safer lagoon areas, and hence to the foundation of Venice.