The Ottoman Empire made good use of cannon as siege artillery. Sixty-eight super-sized bombards were used by Mehmed the Conqueror to capture Constantinople in 1453. Jim Bradbury argues that Urban, a Hungarian cannon engineer, introduced this cannon from Central Europe to the Ottoman realm; according to Paul Hammer, however, it could have been introduced from other Islamic countries which had earlier used cannons. These cannon could fire heavy stone balls a mile, and the sound of their blast could reportedly be heard from a distance of . Shkodëran historian Marin Barleti discusses Turkish bombards at length in his book "De obsidione Scodrensi" (1504), describing the 1478–79 siege of Shkodra in which eleven bombards and two mortars were employed. The Ottomans also used cannon to control passage of ships through the Bosphorus strait. Ottoman cannons also proved effective at stopping crusaders at Varna in 1444 and Kosovo in 1448 despite the presence of European cannon in the former case.