But on the following day they arrayed themselves for the struggle, the Goths thinking to capture Rome by siege without any trouble on account of the great size of the city, and the Romans defending it. Now the wall of the city has fourteen large gates and several smaller ones. And the Goths, being unable with their entire army to envelop the wall on every side, made six fortified camps from which they harassed the portion of the wall containing five gates, from the Flaminian as far as the one called the Praenestine Gate; and all these camps were made by them on the left bank of the Tiber River. Wherefore the barbarians feared lest their enemy, by destroying the bridge which bears the name of Mulvius, should render inaccessible to them all the land on the right bank of the river as far as the sea, and in this way have not the slightest experience of the evils of a siege, and so they fixed a seventh camp across the Tiber in the Plain of Nero, in order that the bridge might be between their two armies. So in this way two other gates came to be exposed to the attacks of the enemy, the Aurelian[96] (which is now named after Peter, the chief of the Apostles of Christ, since he lies not far from there[97]) and the Transtiburtine Gate.[98] Thus the Goths surrounded only about one-half of the wall with their army, but since they were in no direction wholly shut off from the wall by the river, they made attacks upon it throughout its whole extent whenever they wished.Now the way the Romans came to build the city-wall on both sides of the river I shall now proceed to tell. In ancient times the Tiber used to flow alongside the circuit-wall for a considerable distance, even at the place where it is now enclosed. But this ground, on which the wall rises along the stream of the river, is flat and very accessible. And opposite this flat ground, across the Tiber, it happens that there is a great hill[99] where all the mills of the city have been built from of old, because much water is brought by an aqueduct to the crest of the hill, and rushes thence down the incline with great force. For this reason the ancient Romans[100] determined to surround the hill and the river bank near it with a wall, so that it might never be possible for an enemy to destroy the mills, and crossing the river, to carry on operations with ease against the circuit-wall of the city. So they decided to span the river at this point with a bridge, and to attach it to the wall; and by building many houses in the district across the river they caused the stream of the Tiber to be in the middle of the city. So much then for this.And the Goths dug deep trenches about all their camps, and heaped up the earth, which they took out from them, on the inner side of the trenches, making this bank exceedingly high, and they planted great numbers of sharp stakes on the top, thus making all their camps in no way inferior to fortified strongholds. And the camp in the Plain of Nero was commanded by Marcias (for he had by now arrived from Gaul with his followers, with whom he was encamped there), and the rest of the camps were commanded by Vittigis with five others; for there was one commander for each camp. So the Goths, having taken their positions in this way, tore open all the aqueducts, so that no water at all might enter the city from them. Now the aqueducts of Rome are fourteen in number, and were made of baked brick by the men of old, being of such breadth and height that it is possible for a man on horseback to ride in them.[101] And Belisarius arranged for the defence of the city in the following manner. He himself held the small Pincian Gate and the gate next to this on the right, which is named the Salarian. For at these gates the circuit-wall was assailable, and at the same time it was possible for the Romans to go out from them against the enemy. The Praenestine Gate he gave to Bessas. And at the Flaminian, which is on the other side of the Pincian, he put Constantinus in command, having previously closed the gates and blocked them up most securely by building a wall of great stones on the inside, so that it might be impossible for anyone to open them. For since one of the camps was very near, he feared least some secret plot against the city should be made there by the enemy. And the remaining gates he ordered the commanders of the infantry forces to keep under guard. And he closed each of the aqueducts as securely as possible by filling their channels with masonry for a considerable distance, to prevent anyone from entering through them from the outside to do mischief.But after the aqueducts had been broken open, as I have stated, the water no longer worked the mills, and the Romans were quite unable to operate them with any kind of animals owing to the scarcity of all food in time of siege; indeed they were scarcely able to provide for the horses which were indispensable to them. And so Belisarius hit upon the following device. Just below the bridge[102] which I lately mentioned as being connected with the circuit-wall, he fastened ropes from the two banks of the river and stretched them as tight as he could, and then attached to them two boats side by side and two feet apart, where the flow of the water comes down from the arch of the bridge with the greatest force, and placing two mills on either boat, he hung between them the mechanism by which mills are customarily turned. And below these he fastened other boats, each attached to the one next behind in order, and he set the water-wheels between them in the same manner for a great distance. So by the force of the flowing water all the wheels, one after the other, were made to revolve independently, and thus they worked the mills with which they were connected and ground sufficient flour for the city. Now when the enemy learned this from the deserters, they destroyed the wheels in the following manner. They gathered large trees and bodies of Romans newly slain and kept throwing them into the river; and the most of these were carried with the current between the boats and broke off the mill-wheels. But Belisarius, observing what was being done, contrived the following device against it. He fastened above the bridge long iron chains, which reached completely across the Tiber. All the objects which the river brought down struck upon these chains, and gathered there and went no farther. And those to whom this work was assigned kept pulling out these objects as they came and bore them to the land. And Belisarius did this, not so much on account of the mills, as because he began to think with alarm that the enemy might get inside the bridge at this point with many boats and be in the middle of the city before their presence became known. Thus the barbarians abandoned the attempt, since they met with no success in it. And thereafter the Romans continued to use these mills; but they were entirely excluded from the baths because of the scarcity of water. However, they had sufficient water to drink, since even for those who lived very far from the river it was possible to draw water from wells. But as for the sewers, which carry out from the city whatever is unclean, Belisarius was not forced to devise any plan of safety, for they all discharge into the Tiber River, and therefore it was impossible for any plot to be made against the city by the enemy in connection with them.