On April 7 Mahomet’s army had taken up its position along the whole four miles length of the landward walls from the Marmora to the Golden Horn, and with the aid of the fleet prevented all access to or egress from the city. But the men in it had made up their minds to hold it or to die. They began on the first day of the siege to make the best show they could. At the emperor’s request, but also at their own desire, the crews of the galleys under Trevisano and of two others, numbering in all a thousand men, landed and marched along the whole length of the landward walls in presence of the enemy with the object of proving to the Turks that they would have to fight Venetians as well as Greeks. On the 9th the ships in the harbour were drawn up in battle array, ten being at the boom and seventeen in reserve further within the harbour. The Turkish army on the 11th placed its guns in position before the walls. [Sidenote: Cannonading commences April 12.] On the 12th the batteries began playing against the walls and, with ceaseless monotony, day and night the discharge of these new machines was heard throughout the city during the next six days. Their immediate effect soon showed that the walls, solid as they had proved themselves in a score of former sieges, were not sufficiently strong to resist the new invention. The huge balls, fired from a short distance amid a cloud of the blackest smoke, making a terrible roar and breaking into a thousand pieces as they struck the walls, so damaged them that they required daily and constant repair. The narratives of those present agree in representing the defenders from the very commencement of the bombardment as being constantly engaged in repairing the injury done by these ‘takers of cities.’ Large and unwieldy as they were, unmounted and half buried amid the stones and beams by which they were kept in position, they were yet engines of destruction such as the world had never seen. Planted on the very edge of the foss and requiring such management and care that the largest could only be fired seven times a day, they gave proof within a week of their employment that they could destroy slowly but surely the walls which had stood since the reign of the younger Theodosius. The defenders in vain suspended bales of wool and tried other means of lessening the damage. All they could accomplish was to repair and strengthen the damaged portions as rapidly as possible. [Sidenote: Damage done by cannon by April 18.]