Around this time the Ottoman naval fleet developed, such that they were able to challenge Venice, a naval power. They also attempted to reconquer the Balkans. By the time of Mehmed I's grandson, Mehmed II (ruled 1444–1446; 1451–1481), the Ottomans could lay siege to Constantinople, the capital of Byzantium. A factor in this siege was the use of muskets and large cannons introduced by the Ottomans. The Byzantine fortress succumbed in 1453, after 54 days of siege. Without its capital the Byzantine Empire disintegrated. The future successes of the Ottomans and later empires would depend upon the exploitation of gunpowder.