Since 1645, Venice and the Ottoman Empire had been at war over the possession of the island of Crete. Ottoman forces had captured most of the island in the early years of the war, but were unable to seize its capital, the heavily fortified city of Candia (modern Heraklion). The Venetians, superior at sea, endeavoured to cut off the supplies and reinforcements to the Ottoman army, and attempted several times to blockade the Straits of the Dardanelles, through which the Ottoman fleet had to sail to reach the Aegean Sea from its base around Constantinople.