The city was founded as a result of the influx of refugees into
the marshes of the Po estuary following the invasion of northern
Italy by the Lombards in 568. In the mid-8th century, the
Venetians resisted the empire-building efforts of Pepin III and
remained subject to the Byzantine Empire, at least
theoretically. As the community continued to develop and as
Byzantine power waned, an increasingly anti-Eastern character
emerged, leading to the growth of autonomy and eventual
independence. Venice was a city state (an Italian thalassocracy
or Repubblica Marinara, the other three being Genoa, Pisa, and
Amalfi). Its strategic position at head of the Adriatic made
Venetian naval and commercial power almost invulnerable. In the
12th century the essentials for the power of Venice were laid:
the Venetian Arsenal was under construction in 1104; Venice
wrested control of the Brenner pass from Verona in 1178, opening
a lifeline to silver from Germany; the last autocratic doge,
Vitale Michiele, died in 1172. The Republic