This, then, would have been their way of fighting when they met in the open field. It was a different matter when they came to the assault of great cities, especially such as Babylon and Nineveh, which were surrounded and protected, as we know, by walls of vast height and thickness. The walls of Nineveh, for instance, were so broad, even on the top, that three chariots could be driven along them, one beside the other, and of course the width at the bottom must have been very much larger. They had the material very ready at hand for the making of these immense walls--in Babylonia and Assyria at all events. They had abundance of clay, and for the greater part of the walls they used the sun-dried bricks. But for the lower parts, which had to bear the weight, they probably used harder bricks, burnt in the kilns, for there are engravings of soldiers with some kind of battering-ram hammering at the bricks from the lower part of the wall of a city which they are attacking. The diggers would be protected, by a shield held over their heads, from the missiles sent down from the wall above. [Sidenote: Against a walled city] Then they had ladders for the scaling of these walls when they made the attack. But of course the attackers down below would be at a great disadvantage compared with the defenders on top of the wall. They would have a much better chance if by any means they could hoist themselves up to something like the same height as the defenders. And this they {93} contrived to do by making movable towers of wood, on wheels, which could be pushed along by men who were more or less protected by the towers themselves from the people shooting at them from the top of the wall. On the towers would be bowmen who would shoot at the men on the wall, the shooters in the tower being protected by the walls, except in so far as they had to show themselves in order to shoot their arrows or throw their short spears. [Illustration: A BATTERING-RAM.] Another way that they had of hoisting themselves to the same height as the defenders was to build a mound outside the walls. I suppose the earth, as {94} they threw it up, would protect the builders against the arrows shot from the wall. And then, when they had raised the mound high enough, they would sometimes wheel their towers to the top of this, and so it may be that, from the towers on top of the mound, they may actually have had an advantage in height over the defenders on the walls. That would give the opportunity for their own fellow-soldiers below to set up the ladders and attempt the scaling of the walls.