The Ottoman army set out from Adrianople at the beginning of March; and on the sixth of April Mahomet pitched his tent before the gate of St. Romanus. The signal for battle was speedily given on both sides. In the early days of the siege, the Greeks and the Turks displayed all that the art of war had invented or perfected among the ancients and moderns. Among his formidable preparations, Mahomet had not neglected artillery, the use of which was then spread through the West. One of his cannons, founded under his own eyes at Adrianople, was of such gigantic proportions, that three hundred oxen dragged it along with difficulty, and it launched a ball of seven hundred quintals (seven hundred pounds weight) to a distance of more than six hundred toises (six hundred fathoms). Almost all the historians of the time speak of this terrible instrument of war, but say very little of the effect it produced in the field of battle. On examining with care the accounts of contemporaries, and particularly the descriptions they have left us of these enormous machines of bronze, which they had so much trouble to move, we feel persuaded that at the siege of Byzantium the Ottoman artillery inspired more fright and surprise than it did execution. The Turks showed very little skill or zeal in seconding the Frank engineers and artillerymen whom Mahomet had taken into his service; and it was a great blessing for Christendom that so powerful a discovery was not perfected at once in the hands of barbarians, whom Europe could not have resisted if they had joined this new force to the advantages they already possessed in war.