The eastern front had for a long time depended for its safety on a single wall reinforced by a moat, but Sennacherib, deeming it insufficiently protected against a sudden attack, had piled up obstacles in front of it, so that it now presented a truly formidable appearance. It was skirted throughout its whole length by a main rampart, 5400 yards long, which described a gentle curve from north to south, and rose to a height of about 50 feet, being protected by two small forts placed close to the main gates. The fosse did not run along the foot of the wall, but at a distance of about fifty yards in front of it, and was at least some 20 feet deep and over 150 feet in width. It was divided into two unequal segments by the Khuzur: three large sluice-gates built on a level with the wall and the two escarpments allowed the river to be dammed back, so that its waters could be diverted into the fosse and thus keep it full in case of siege. In front of each segment was a kind of demi-lune, and--as though this was not precaution enough--two walls, each over 4300 yards long, were built in front of the demi-lunes, the ditch which separated them being connected at one end with the Khuzur, and allowed to empty itself into a stream on the south. The number of inhabitants sheltered behind these defences was perhaps 300,000 souls;* each separate quarter of the city was enclosed by ramparts, thus forming, as it were, a small independent town, which had to be besieged and captured after a passage had been cut through the outer lines of defence. * Jones and G. Rawlinson credit Nineveh with a population of not more than 175,000.