Gallipoli became the main crossing point for the Ottoman armies moving between Europe and Asia, protected by the Ottoman navy, which had its main base in the city. Sultan Bayezid I () refortified Gallipoli and strengthened its walls and harbour defences, but initially, the weak Ottoman fleet remained incapable of fully controlling passage of the Dardanelles, especially when confronted by the Venetians. As a result, during the Ottoman–Venetian War (1463–1479) the straits' defences were strengthened by two new fortresses, and the Ottoman imperial arsenal was established in Istanbul itself. Gallipoli remained the main base of the Ottoman fleet until 1515, when it was moved to Istanbul. After this it began to lose its military importance, but remained a major commercial centre as the most important crossing-point between Asia and Europe.