Even though the Ottomans held nearly universal control over the island, the siege of Candia would go on for 21 years. The situation was complicated by naval engagements against Christian fleets in the Aegean, as well as internal political turmoil including the deposition of Sultan Ibrahim in favor of his son, Mehmed IV. During this same period, the Ottoman-Venetian war raged on several other fronts, notably a campaign in Dalmatia and several Venetian attempts to blockade the Dardanelles. In 1666, after the resolution of several other fronts, the Ottomans dispatched sizeable reinforcements towards Crete, under the personal command of Grand Vizier Köprülü Fazıl Ahmed Pasha. Over the final two years of the siege, the Venetians, bolstered by Ottoman infighting and expecting reinforcements from France, refused several offers of peace treaties. After a failed attempt by French soldiers under the Duke of Beaufort to break the Ottoman siege, the city surrendered on 5 September 1669. With this victory, the Ottomans secured their first major territorial gain in almost a century, and simultaneously ended 500 years of Venetian rule over Crete.