The siege has been running in full force for over a week now.
Ottoman troops began to take up their positions along the walls during the first week of April. The Sultan himself erected his tent north of the civil Gate of Saint Romanos, near the river Lycus, facing Military Gate of St. Romanos. A defensive trench was dug in front of the Ottoman units, and the earth from it was piled on the city side and on top of which a palisade was erected.
On 6 April the Sultan’s cannon started their bombardment of the city’s defences after the Emperor had turned down the obligatory Islamic offer to spare the lives of the inhabitants if they surrendered. The Turkish artillery included a massive cannon cast on Mehmet’s specific orders. It was designed for him by an itinerant engineer named Urban who was appointed by the Sultan in 1452. He may have been either German or Hungarian and was an expert armourer.
Urban had previously approached the Emperor of the Romans with an offer to design and build cannon for the Empire. However, Constantine had to send him away empty handed; the Empire was by that time too impoverished to employ him and could not obtain the required raw materials. We know history turns on many small events, in this case a recruiting decision? How different might it have been had Urban offered his services elsewhere in Europe and not then to the Ottomans. It could be said that the Empire was now in terminal decline at this stage and the outcome was almost inevitable. If the Fall had not happened in 1453 it would most likely have occurred sometime in the next few years.
What was so special about Urban’s cannon? He had already built one large cannon for the Sultan which was placed at his newly constructed fortress of Boghaz Kesen, meaning “the cutter of the Strait” or “of the Throat” (referring to the narrowest point of the Bosphorus). The Byzantines called this Rumeli Hisar, or “The castle of Romeland”, which was a pretty good name as it was the medieval equivalent of the Sultan parking his tank on the Emperor’s lawn as it was just a few miles from the city. Mehmet could do as he pleased and respected no treaties. The fortress cannon was used to enforce the Sultan’s new tax on every ship that passed through the straits. On one occasion a Venetian ship tried to run this blockade and was sunk. We may think of medieval artillery as inaccurate, but to take out a fast moving ship, captained by arguably the ablest sailors in the Mediterranean at the time, required reliable weaponry and very good gunnery skills. The Ottoman gunners should not be underestimated.
The new cannon (and we don’t appear to have a name for this – typically one-off, unwieldy, but morale crushing weapons have names like “Deliverer of Death” or even “Supergun” but nothing appears to survive) was apparently nearly twenty-eight feet long, its barrel was two and a half feet in diameter at the business end, and the bronze was at least eight inches thick. During field tests (when the local inhabitants were warned not to be alarmed about the noise!) it fired a cannon ball weighing 1,340 pounds well over a mile before it buried itself six feet in the ground. The noise could be heard over ten miles away.
This monster cannon had seven hundred men to service and support it (you can bet they gave it a name); and fifteen pairs of oxen to haul it. Roads and bridges had to be strengthened along the route from the Sultan’s foundry in Adrianople. Such a combined artillery force had never before been seen in the East, although it had been fairly common in Western Europe for the last one hundred years.
The bombardment that started on 6 April was unprecedented. By the end of the first day a section of the wall near the Charisius Gate was reduced to rubble and Turkish soldiers attempted to storm the walls. Despite repeated charges they were driven back, and night fell bringing a degree of peace. The defenders would have used a combination of their own smaller cannon, bows, crossbows, ballistae type weapons, and the advantages of the defensive system offered by the Walls of Theodosius to canalize the enemy into killing zones where they had very little opportunity to manoeuvre. The inner terrace between the inner and outer walls was called the perivolos and accommodated the soldiers who defended the outer wall. It was between 50 and 64 feet wide. Beyond lay the outer wall, which was a modest structure compared with the inner wall. It was in this zone that most of the killing, which would have been hand to hand at some points, would have taken place. The Sultan’s troops would have been cut down in their companies whilst the defenders suffered few casualties.
By 12 April an Ottoman fleet arrived which included approximately 200 ships of various sizes. The fleet established a sea blockade sealing the Roman capital from the sea. The city was now completely surrounded.
With the siege now established in full, a pattern now emerged. Over the coming weeks the Turks would create breaches by day only for the defenders to rebuild the walls and towers overnight, sometimes using brick and stone, at other times using wooden stockades and earth filled barrels. With his 100,000 men the Sultan could rest his men and attack in relays. The defenders had no such opportunity fighting by day, patrolling and rebuilding by night, they must have reached a state of exhaustion. But on 6 April they must have been relieved just to have survived the first day, and it was the Sultan who had suffered more casualties and had to rethink his plans. This he did, and displayed genuine tactical agility and improvisation as we shall see in the coming weeks.
As the siege entered into its second week Constantine and his captains waited for news of relief troops from the West, uncertain if any were on their way.