The first of the three empires to acquire gunpowder weapons was the Ottoman Empire. By the 14th century, the Ottomans had adopted gunpowder artillery. The adoption of the gunpowder weapons by the Ottomans was so rapid that they "preceded both their European and Middle Eastern adversaries in establishing centralized and permanent troops specialized in the manufacturing and handling of firearms." But it was their use of artillery that shocked their adversaries and impelled the other two Islamic empires to accelerate their weapons programs. The Ottomans had artillery at least by the reign of Bayezid I and used them in the sieges of Constantinople in 1399 and 1402. They finally proved their worth as siege engines in the successful siege of Salonica in 1430. The Ottomans employed Middle-Eastern as well as European foundries to cast their cannons, and by the siege of Constantinople in 1453, they had large enough cannons to batter the walls of the city, to the surprise of the defenders.