 Complete the following phrase:  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 Is grandson, Mehmed II ruled 14441446; 14511481, 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 