Vitiges when he arrived saw that he could not take the city by a _coup de main_ and must make a regular siege. The skill of the Goths, accustomed to fight in the open field, was of little avail in laying siege to a city, and Vitiges, overlooking this fact, staked his entire kingdom against the walls of Rome, with the result that his heroic people here found their overthrow. The Goths formed six entrenched camps before these defences, all on the left side of the river; a seventh they erected on the right bank of the Tiber on the Neronian Field, or the plain which stretches under Monte Mario from the Vatican Hill as far as the Milvian bridge. They thus not only protected the bridge itself but at the same time threatened the bridge of Hadrian and the entrance to the city through the inner gate of Aurelian. This gate, already named St. Peter’s, stood outside the bridge of Hadrian and beyond the wall which, from the Porta Flaminia on the inner side of the river, surrounded the field of Mars. Vitiges at length was ready to deliver a decisive assault. Wooden towers sufficiently high to overlook the defences, were set on strong wheels; projecting battering rams of iron were hung by chains to be thrust against the walls, each manned by fifty men, and long scaling ladders were constructed to be attached to the battlements. To these preparations (at the rude simplicity of which modern military science may smile) Belisarius opposed measures all his own. He set upon the walls skilfully contrived catapults or balistae, and great stone slings (_onagri_) called “wild asses” were constructed to throw a bolt with such force as to pin a mail-clad man fast to a tree. The gates were themselves defended with so-called “wolves” or drawbridges fashioned out of heavy beams and furnished with iron pins which were to be released at a given moment to fall on the assailants with overwhelming force.