Siege of Candia The Siege of Candia ( modern Heraklion , Crete ) was a military conflict in which Ottoman forces besieged the Venetian - ruled city and were ultimately victorious . Lasting from 1648 to 1669 , it was the longest siege in history . Background . In the 17th century , Venice ' s power in the Mediterranean was waning , as Ottoman power grew . The Venetian Republic believed that the Ottomans would use any excuse to pursue further hostilities . In 1644 , the Knights of Malta attacked an Ottoman convoy on its way from Alexandria to Constantinople . They landed at Candia with the loot , which included part of the Sultan ' s harem , returning from a pilgrimage to Mecca . In response , 60 , 000 Ottoman troops led by Yussuf Pasha disembarked on Venetian Crete and occupied La Canea ( modern Chania ) and Rettimo ( modern Rethimno ) . Both of these cities took two months each to conquer . Between 1645 and 1648 , the Ottomans occupied the rest of the island and prepared to take the capital , Candia . Siege . The siege of Candia began in May 1648 . The Ottomans spent three months laying siege to the city , cutting off the water supply , and disrupting Venice ' s sea lanes to the city . For the next 16 years , they would bombard the city to little effect . The Venetians , in turn , sought to blockade the Ottoman - held Dardanelles to prevent the resupply of the Ottoman expeditionary force on Crete . This effort led to a series of naval actions . On 21 June 1655 and 26 August 1656 , the Venetians were victorious , although the Venetian commander , Lorenzo Marcello , was killed in the latter engagement . However on 17 – 19 July 1657 , the Ottoman navy soundly defeated the Venetians and the Venetian captain , Lazzaro Mocenigo , was killed by a falling mast . Venice received more aid from other western European states after the 7 November 1659 " Treaty of the Pyrenees " and the consequent peace between France and Spain . However , the Peace of Vasvár ( August 1664 ) released additional Ottoman forces for action against the Venetians in Candia . In 1666 , a Venetian attempt to recapture La Canea failed . The following year , Colonel Andrea Barozzi , a Venetian military engineer , defected to the Ottomans and gave them information on weak spots in Candia ' s fortifications . In 1669 , a French land / sea expedition under Mocenigo not only failed to lift the siege , but also lost on 24 July the fleet ' s vice - flagship , " La Thérèse " a 900 - ton French warship armed with 58 cannons , to an accidental explosion . This dual disaster was devastating to the morale of the city ' s defenders . Apparently chastened by their failed relief effort and the loss of so valuable a warship , the French abandoned Candia in August 1669 leaving Captain General Francesco Morosini , the commander of Venetian forces , with only 3 , 600 fit men and scant supplies to defend the fortress . He , therefore , accepted terms and surrendered to Ahmed Köprülü , the Grand Vizier of Albanian origin of the Ottoman Empire of on 27 September 1669 . However , his surrender without first receiving authorization to do so from the Venetian Senate made Morosini a controversial figure in Venice for some years afterward . As part of the surrender terms , all Christians were allowed to leave Candia with whatever they could carry while Venice retained possession of Gramvousa , Souda and Spinalonga , fortified islands that shielded natural harbors where Venetian ships could stop during their voyages to the eastern Mediterranean . After Candia ' s fall , the Venetians somewhat offset their defeat by expanding their holdings in Dalmatia . It is said that when news of Candia ' s fall reached Pope Clement IX in October he immediately fell ill and , two months later , died . In fiction . The Siege of Candia is an important part of the background to the historical novel " An Instance of the Fingerpost " , where a major protagonist is a Venetian veteran of that siege and several plot developments become clear through extensive flashbacks to the Candia events .