In "City of Fortune: How Venice Ruled the Seas", Roger Crowley covers
the rise and fall of one of the first maritime empires. The case is
fascinating. Venice's major advanatage is protection against invasion
from land and from sea. Its marshy Venetian Lagoon forms something of
Italian Everglades and originally created a refuge to the inhabitants
of nearby Roman cities against barbarian raids. On the see side,
shalow waters require good knowledge of waterways and preclude massive
assault from the sea.  Yet, the place has no natural resource. Even
drinking water had to be either collected during rains or brought from
the outside.

However, Venice was able to build a powerful empire in the Eastern
Mediterranean. The book follows its assent from the time of Orseolo
eradication of Croatian pirates in the year 1000 that freed Venice's
trade routes, through blind dodge Dandolo using crusaiders to quash
the rival city-states and then sack Byzantium in the 13-th century,
and then to the empire's decline due to rising Ottoman power and
Portugese discovery of alternative spice route that undermined
Venice's advantage in the trade with the East and shifted world trade
elsewhere.

It is intersting how Venice was in effect a collecitive endeavor of
merchant capitalism. The state's major effort, its (pardon my French)
reison d'etre, was to secure advantageous trading terms and conditions
for its merchants. Venetians cared little for land conquest and
instead tried to obtain monopolies, ports, trading stations and
naval bases to control strategic seaways.