The military history of the Republic of Venice started shortly after its founding, spanning a period from the 9th century until the Republic's fall in the 18th century.
Military conflict between Venice and Italy began in the early 9th century with the intervention of Charlemagne's son King Pepin of Italy into Venice, which resulted in a failed six-month siege.
Venice first became a major military power in the 13th century during the Fourth Crusade, where Venetian troops participated in the successful siege and conquest of Constantinople, gaining vast territories and other war spoils. Later in the century, Venice commenced a series of wars with the Republic of Genoa and a number of its allies for dominance in the Mediterranean Sea. With the rise of the Ottoman Empire, the Republic lost its territories in the east as Cyprus and Venetian strongholds in Morea were occupied; at the same time, the rise of the Visconti of Milan drew Venice into the condottiere warfare of Italy.
The 14th century saw Venice successfully siege the northern Dalmatian town of Zadar with some 20,000 troops, as part of the Croatian-Venetian wars.
Bereft of her Mediterranean possessions, Venice turned to conquest on the Italian mainland, which brought it into conflict with Milan and the Papacy. Venetian participation in the Italian Wars eventually resulted in the War of the League of Cambrai, where Venice was nearly reduced. Following the War of the League of Cognac, Venice played little further role in mainland warfare. She continued to fight naval wars against the Ottomans, however, culminating in the victory at the Battle of Lepanto.
The beginning of the 17th century saw a war against Austria and others over Uskok pirates. In the latter half of the 17th century, further Ottoman aspirations to capture Crete caused another protracted period of warfare, known as the Cretan War. The twenty-year Siege of Candia was followed by her involvement in the Great Turkish War, where the Republic briefly regained the Morea, only to return it some years later. The Republic of Venice was finally drawn into European warfare with Napoleon's invasion of Italy; unable to resist his armies, she was forced to surrender and become a French tributary state.